US3855578

Extracted document text. Layout, formulas and symbols may not survive extraction; consult the preserved PDF for the original presentation.

Text extraction covers 7 pages, including 7 transcribed by optical character recognition.

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United. States Patent 1191

Watson

ui) ~~: 3,855,578
[45] Dec. 17, 1974

[54] HOLOPHONE INFORMATION STORING

AND/OR PROCESSING DEVICE

{75} Inventor: Christopher John Hamilton Watson,

Oxford, England

[73] Assignee: United Kingdom Atomic Energy

Authority, London, England
[22] Filed: Mar. 8, 1971
[21] Appl. No.: 121,920

[30] Foreign Application Priority Data
Mar. 11,1971 Great Britain............... 11777/70
[52] U.S. CL. - 340/173 NC, 340/172.5

({S1] Int. Cl...
(58]

{56] References Cited
UNITED STATES PATENTS

2,887,673 SI1959 0 Hahn oe eeeeeneeee 340/173 NI

. G1le 13/00
340/173 NI

3,215,988 11/1965 Clapp
3,324,461 6/1967 Kaplan

340/173 NI
340/173 NI

Primary Examiner—Terrell W. Fears
Attorney, Agent, or Firm—Larson, Taylor & Hinds

{57] ABSTRACT

Certain natural physical systems, such as a collision-
less plasma excited by a sequence of spatially periodic
electrostatic pulses, or a material possessing net nu-
clear or electron spin in an external magnetic field,
are adapted for information processing, for example
for searching a mass of stored information for the
presence of information related to a particular portion
of information, or “cue.”

7 Claims, 3 Drawing Figures

YNPOT
LCE TS A-

DETECTION
VEN TS —

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PATENTED OEC 1 7197

4

3,855,578

STOCLLD |W 3S CGE
SVEN AL SIGNAL
STOKE SbAphyt STOCE
72
Z
MATCHING
WIT
I
HOLOPHONE|—74
MATERLAL
1 .
Monae LA. A
IM
LUT
L AEE 76
LS = = 7 a)
; OUTPUT
G aA Wide 6 STORE
79
aw a 419.5.
CS a af 2
L 2
wv cy
il a
27
Wa AN Mf rf
NYT
CSCW TEL. =
DEFECTION | Bis

VRC TS —.

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3,855,578

1

HOLOPHONE INFORMATION STORING AND/OR
PROCESSING DEVICE

BACKGROUND OF THE INVENTION

The invention relates to a holophone information
storing and/or processing device.

The holophone is the temporal analogue of the holo-
graph, in the sense that it stores information, presented
to it in the form of a time-sequence, in a temporally
non-local manner, just as a holograph stores informa-
tion, presented in the form of a spatial array, in a spa-
tially non-local manner.

Theoretical properties of a holophone viewed as a
black box are discussed by D. J. Willshaw and H. C.
Longuet-Higgins in Machine Intelligence No. 4 (1969),
page 349.

Three properties mentioned of particular interest are
as follows:

1. If an input signal is recorded in the holophone and

a part of this signal re-injected, a signal emerges
which is the continuation of the input signal from
the part re-injected.

2. If several signals are recorded in the holophone, an
input cue from one of the signals will evoke the
continuation of that one signal.

3. The holophone may be used for detecting the oc-
currence of a given segment in the course of a long
signal. For this, the segment of interest is recorded
on the holophone followed by a strong pulse. The
long signal is then played into the holophone when
a pulse emerges from the holophone immediately
after an occurrence of the recorded segment.

An implementation is described in the form of a bank
of narrow-pass filters connected in parallel to an input
channel, and also connected in parallel, through ampli-
fiers of variable gain, to an output channel.

However, this implementation does not at present ap-
Pear to be a plausible practical device for recording in-
formation sequences of useful length at reasonable
speed and cost.

The present invention is based upon the appreciation
that certain natural physical systems (hereinafter re-
ferred to as holophone materials) exhibit physical phe-
nomena capable of holophonic behaviour in response
to appropriately generated input signals. Specifically,
one example of such a holophone material is a colli-
sionless plasma, excited by a sequence of spatially peri-
odic electrostatic pulses. Other examples of holophone
materials are materials possessing net nuclear spin,
such as water or paraffin, or materials possessing un-
paired electron spin, in association with means for ap-
plying radiofrequency magnetic field pulses at a fre-
quency close to the nuclear or electron (as the case
may be) spin resonance frequency in an external mag-
netic field.

A further appreciation, upon which the present in-
vention is based, has emerged from analysis showing
that the general principles (1) to (3) above apply to a
series of pulsed signals which are coded, for example,
in a binary coding system, and that, whilst the noise
problem (as discussed by Willshaw and Longuet-
Higgins in the above-mentioned article) is present, the
output signals are susceptible of “cleaning up.”

SUMMARY OF THE INVENTION
The invention provides a holophone information

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storing and/or processing device comprising generator
means for generating coded signal pulses, representing
information, in a form for causing a systematic distur-
bance to the motion of elements within a holophone
material, which elements possess or are caused to ac-
quire a natural periodicity in their motion, control
means operative to cause the generator means to sup-
ply in succession to the holophone material a series of
pulses representing a store of information and a series
of pulses representing a portion of information, and
means for detecting subsequent echo waveforms emit-
ted by the holophone material.

In one arrangement according to the invention the
holophone material comprises a collisionless plasma
confined within a plasma confinement system such as
has been developed in the context of research into ther-
monuclear fusion. As discussed in more detail below,
the confined plasma for this application as a holophone
material differs from that involved in thermonuclear
fusion research in being desirably a plasma at as low a
temperature as is practicable. In this arrangement the
generator means preferably comprises a matching unit
for converting signal pulses into electrostatic pulses in
the plasma, each of which electrostatic pulses has a
spatial periodicity within the plasma, a stored. signal
source, such as a computer type of backing store, of
coded signal pulses representing stored information, a
cue signal source of coded signal pulses representing a
portion of information, and means for connecting the
stored signal source and the cue signal source to the
matching unit to supply thereto their respective series
of signal pulses in succession.

In another arrangement according to the invention
the holophone material comprises a material Possessing
nuclear or electron spin. In this case the generator
means preferably comprises a matching unit for con-
verting signal pulses into radiofrequency electromag-
netic pulses, a stored signal source, such as a computer
type of backing store, of coded signal pulses represent-
ing stored information, a cue signal source of coded sig-
nal pulses representing a portion of information, means
for connecting the stored signal source and the cue sig-
nal source to the matching unit to supply thereto their
respective series of signal pulses in succession, there
being provided means for applying a fixed external
magnetic field to the holophone material, the fre-
quency of the electromagnetic pulses generated by the
matching unit being close to the nuclear or electron (as
the case may be) spin resonance frequency in the said
external magnetic field.

Preferably the aforesaid means for detecting subse-
quent echo waveforms emitted by the holophone mate-
rial includes a clarifier for improving the observed sig-
nal to noise ratio. In one form of the clarifier comprises
means for detecting the sign of the signal output from
a monitoring unit, which detects the output signals
from the holophone material.

The invention further provides a holophone informa-
tion storing and/or processing device comprising, as
holophone material, a material possessing nuclear or
electron spin, means for applying a fixed external mag-
netic field to the holophone material, generator means
for generating signals, representing information, in a
form of systematically disturbing the alignment of the
nuclear or electron spins with the said external mag-
netic field, and means for detecting echo waveforms
emitted by the holophone material. In operation a first

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signal representing information is supplied to the holo-
phone material followed by a second signal to be com-
pared with the first signal. If the second signal contains
a portion of the first signal, an echo will be emitted
from the holophone material, which echo corresponds
with the continuation of the first signal from the por-
tion represented by the second signal. The application
of this arrangement to, for example, speech recognition
will thus be appreciated.

BRIEF DESCRIPTION OF THE DRAWINGS

Specific constructions of device embodying the in-
vention will now be described by way of example with
reference to the accompanying drawings, in which:

FIG. 1 is a block diagram of essential elements of a
device,

FIG. 2 is a diagrammatic representation of a part of
one form of device, and

FIG. 3 is a diagrammatic representation of a part of
another form of device.

DESCRIPTION OF PREFERRED EMBODIMENTS

Two forms of holophone material are described in
these examples: a collisionless plasma and a nuclear
spin material. It will be appreciated that a system em-
ploying electron spin material may be derived from its
close analogy with the nuclear spin system.

In both the systems discussed the time during which
the holophone retains the information fed into it is
short. In the plasma system the limit is set by the means
collision time of the electrons in the plasma and the
time after which the electrons are lost from the con-
fined plasma to the surrounding walls. Both of these

times must be longer than the time during which the -

holophone is required to remember a given information
sequence. In the nuclear spin system, the limit is set by
the relaxation time or the loss of spin phase coherence
due to self-diffusion of molecules in liquids.

Whilst the holophone materials of these examples do
store information, the period is so short that the materi-
als are used in conjunction with a backing store and the
holophone device may therefore be regarded as a signal
processing system.

The technique may best be described with reference
to FIG. 1, supposing that it is desired to search a mass
of stored information for presence of information re-
lated to a particular portion of information or “cue.”

The mass of stored information is stored in a stored
signal store 11, which may conveniently comprise a
suitable computer store. This information is fed out in
a sequence of binary coded pulses to a matching unit
12. The matching unit converts the store output pulses
into pulses suitable for injection into the holophone
material 14 for exciting its holophonic response. Imme-
diately after completion of this operation, a cue signal
is fed into the matching unit 12 from a cue signal store
13. If any part of the cue signal corresponds with a part
of the stored information, echo signals will emerge
from the holophone material 14 which correspond to
the whole of the stored information signals starting
from the first point of correspondence with the cue sig-
nal.

The echo signals are detected by a monitoring unit 15
and fed via a clarifier 16 and rematching unit 17 to an
output store 18.

Theoretical analysis indicates that the echo signal is
very noisy, but the form of the echo signal equation in-

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dicates possiblities for cleaning the signal and it has
been found that a dramatic improvement in signal to
noise ratio may be achieved simply by attaching signifi-
cance to the sign of the output echo signal and not its
magnitude. Assuming a total of 100 signal pulses have
been injected of which 10 are cue signals, this tech-
nique for improving the signal to noise ratio leads to a
substantial agreement between the recorded and play-
back sequences. It is envisaged that more sophisticated
“cleaning up” procedures would improve playback
clarity further.

The rematching unit 17 performs a function which is
the inverse of the matching unit 12.

It will thus be seen that the holophone system pro-
posed provides a device capable of searching informa-
tion. A significant advantage which the device provides
is the ability to recognise incomplete information or in-
formation containing inaccuracies. The device is also
fast. There need be no significant delay between feed-
ing in a cue signal and emergence of the echo response.
Whilst it is true that the whole of the information to be
searched has to be fed into the holophone, this is a
comparatively straightforward operation even with a
binary digital pulse code system. Existing technology
would permit this operation at a speed in excess of 100
binary bits per microsecond. Furthermore, when it is
known that a certain section of stored information is to
be searched, it is possible to start transferring the
stored information into the holophone device a short
time before the cue signal is ready. In fact, the stored
information could be repeatedly injected into the holo-
phone device whilst a series of searching operations are
carried out upon it.

It will be appreciated, however, that the device is ca-
pable of other forms of information processing such as
for speech recognition, or for content addressable com-
puter memories. With the collisionless plasma system,
the information is required in a pulse code modulated
form, but conversion of speech or written test to such
a form is a routine procedure and computer-stored in-
formation is already conventionally in binary digital
form. The information may also be in pulse code modu-
lated form in the nuclear or electron spin system, but
this system can also operate upon continuous wave sig-
nals,

In the example employing a collisionless plasma as
holophone material, the electrical signal pulses forming
the output from the backing stores (11, 13) contro! the
excitation of electrostatic waves in an ionised plasma.
The waves should be essentially plane standing waves
such that the electric field E(x,1) = R(t) sin kx where
27/k = d is the wavelength of the wave and R(t) is the
amplitude of the wave at time ¢ as determined by the
electrical pulse sequence applied to the input matching
unit 12 of the holophone device.

Thus, in this example, the motion of electrons in the
plasma is disturbed by the imposed electrostatic stand-
ing wave pattern and the electrons are caused to ac-
quire periodicity in their motion by the spatial periodic-
ity of the standing wave pattern itself.

The dimensions, temperature and density ‘“‘n” of a
suitable plasma are fairly widely variable. The con-
straints are as follows:

The Debye length

An = (4arne/kT) “1
should desirably be comparable with or large compared

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with the wavelength A. This reduces collective plasma
effects which would mask the plasma echoes. In the ex-
pression ‘‘e’’ is the electronic charge, “k” Boltzmann’s
constant, and “‘T” the effective absolute temperature
of the plasma.

Under this condition, to secure sharp output pulses
from the holophone, the temperature of the plasma
must be sufficiently high for the relation

KV At >> 4

to be satisfied where V is the mean velocity of the elec-
trons at the temperature T and At is the time interval
between pulses.

As stated above, the mean collision time 7, for elec-
trons in the plasma and the time 7, after which the elec-
trons are lost from the plasma to the surrounding walls
must both be longer than the time 7,, during which it is
desired to use the holophone to remember a given in-
formation sequence.

This latter requirement suggests that one should seek
the shortest possible interval Ar between pulses. How-
ever, Ar has to be substantially in excess of the duration
81 of each pulse, which itself must also satisfy the re-
quirement

kV 81 << 1

in order that the pulses appear instantaneous to the
electrons. Conveniently one requires

8t < 1/10 Ar

Against this there are, of course, practical limits on
the extent to which 6f can be reduced.

Assuming the lowest feasible plasma temperature is
T, of the order of 0.5 eV, and taking for Ar the shortest
time consistent with the constraints discussed above,
the maximum number of pulses which could be fitted
into a straight plasma would be about 60, if the elec-
trons are assumed lost when they arrive at the longitu-
dinal ends of the plasma within the vacuum vessel. For
this reason, for most applications, it is necessary to em-
ploy a toroidal plasma of small perimeter (<30 cen-
timetres) or to arrange for electrons to be efficiently
reflected back into the plasma before they reach the
longitudinal end walls of the vacuum vessel. Such re-
flection can be readily provided using appropriate elec-
tric fields or magnetic mirror fields. In a known forms
of straight plasma confinement system, called a Q ma-
chine, the longitudinal end walls comprise metal heated
to white heat for ionising gas which is directed onto
them. Confinement in the transverse directions is pro-
vided by a longitudinal magnetic field. It so happens
that, in this system, electric fields exist near the end
walls which reflect back electrons into the plasma. This
serves to increase the effective length of the straight
plasma for the holophone application herein proposed.
With this arrangement, however, provision has to be
made to avoid the information becoming confused
within the system by the end reflections. One way of
making such provision is to arrange for the plasma
length between the reflection planes to be an integral
multiple of the wavelength A, as herein defined.

The length of the plasma column is related to the
presently obtainable lower limit for &f (of the order of
107° seconds) and the wavelength of the electrostatic
pertubation. The following example gives a practical
set of parameters consistent with the above constraints.

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FIG. 2 shows diagrammatically a plasma containment
toroid of major radius R about 3 centimetres and desir-
ably containing the plasma to a minor radius of 3 mil-
limetres with a toroidal magnetic field of 5 kiloGauss
(approximately).

Plasma density is desirably in the range n = 10®-10°
particles/cm?. Too high a density reduces the mean col-
lision time and enhances undesirable coliective effects,
whilst with too low a density the output signals are too
weak.

Summarising, the following approximate design pa-
Tameters are consistent with the above:

dh = Lem)
Te. = 05 eV)
Kvet = 1/3)
kVA 3)
©, = 5.10%
kAy = 0.6)

The confinement system must be such as to allow all
particles to circulate along approximately parallel mag-
netic field lines and must have a confinement time
greater than the maximum time for which the holo-
phone device is to be used in one operation.

To generate the desired electrostatic waves in the
plasma, the matching unit 12 adjusts the amplitude of
the output pulses from the backing store for application
to a digital line indicated diagrammatically at 19, 21 in
FIG. 2.

In practice, the digital line will comprise teeth which
are more closely spaced and extend closer to the minor
axis of the vessel than is indicated by 19, 21 in the dia-
grammatic FIG. 2. That is, the structure will have the
appearance in cross-section of a comb.

In an alternative arrangement, the matching unit gen-
erates pulses of radiofrequency electromagnetic signals
which are used to create a spatially periodic standing
wave which sets up a periodic quasi-potential within
the plasma which operates in a manner exactly analo-
gous to a spatially periodic electrostatic pulse. This
possiblity is explained in an article by Motz and Watson
in Advances in Electronics, Volume 23.

The monitoring unit 15 operates by detecting radio-
frequency scattering off from the periodic density vari-
ation in the plasma. Alternatively the monitoring unit
15 may detect changes in induced charge upon the digi-
tal line 19, 21, In this example employing a plasma as
holophone material, the monitoring device has to dis-
tinguish cyclic waveform pulses (that is pulses having
a complete cycle with a positive phase and a negative
phase) which are initially positive going from cyclic
waveform pulses which are initially negative going.

FIG. 3 illustrates part of the apparatus for the exam-
ple in which the holophone material is a material pos-
sessing nuclear spin. The sample of material is con-
tained in a vessel 22 supported between coil windings
23, which are adapted to impose radiofrequency mag-
netic field signals upon the specimen.

The vessel 22 and coil windings 23 are supported as
a whole between pole pieces 24, 25 of a large electro-
magnet which provides a uniform steady magnetic
field, perpendicular to that of coil windings 23, for
polarising the nuclear magnetic moments prior to injec-
tion of the signal pulses.

This form of apparatus, and the equipment for driv-
ing it, are substantially conventional for experimental
measurements of nuclear magnetic moments. For this

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example, however, the drive circuits are modified to
inject, into the coil windings 23, radiofrequency pulses
of duration &t and corresponding to the binary digital
pulses supplied from the backing stores (11, 13). The
pulse duration &¢ is such that

yH&<<1

where y is the nuclear gyromagnetic ratio and H is the
magnetic gyrofrequency.

The frequency of the pulsed signals is required to be
close to the mean gyrofrequency for spins in the sam-
ple.

Echo signals are detected by the current they induce
in the coil windings 23. The input leads to the coil
windings 23 are shown branched at 26 for connection
to input and detection circuits indicated diagram ati-
cally at 27 and 28 respectively.

Whilst any material, such as water or paraffin, pos-
sessing net nuclear spin may be employed, for applica-
tions in which the holophone device is required to store
information for as long as possible it will be desirable
for the material to have a long relaxation time and
weak self-diffusion.

A system employing material with unpaired electron
spin will be closely comparable with the nuclear spin
system, except that a different value of mean spin gyro-
frequency will be involved.

Suitable systems are, for example:

1, a paramagnetic spin system such as Ce** in lantha-

‘num magnesium nitrate and described by J. A.
Cowen and D. E. Kaplan in Physical Review, Vol.
124, No. 4, November 1961;

2. a ferromagnetic spin system such as yttrium iron
garnet described by D. E. Kaplan in Physical Re-
view Letters, Vol. 14, No. 8, February 1965;

3. a semiconductor spin system such as lithium or
phosphorus doped silicon described by J. P. Gor-
don and K. D. Bowers in Physical Review Letters,
Vol. 1, No. 10, November 1958.

In the nuclear spin and electron spin systems the dis-
turbance to the motion of the spinning elements is
caused by the pulsed radiofrequency signals. The natu-
ral periodicity in the motion is provided by the spin
gyro-motion itself.

The invention is not restricted to the details of the
foregoing example. For instance a system employing
plasma cyclotron echoes may be used as the holophone
material. For this, a plasma is disturbed by radiofre-
quency pulses close to the cyclotron frequency of the
plasma in its confining magnetic field. The echo phe-
nomenon in this case is somewhat similar to that of the
nuclear or electron spin systems.

In alternative systems the plasma may be confined in
an electrostatic potential well, or a magnetic mirror
system. In these cases, a periodic grid structure such as
19, 21 in FIG. 2 is not required because the plasma par-
ticles already possess a natural periodicity in their mo-
tion.

Thus, a simple system of end plates and an intermedi-
ate grid can be employed for injecting the signal pulses.
In these systems, a necessary condition is that the fre-
quency of oscillation of particles in the well is depen-
dent upon the energy of the particles. The apparatus
for such alternative systems may be based upon that de-
scribed by Alfred Y. Wong and Robert J. Taylor in
Physics Review Letters, Volume 23, page 958, 1969,
“Trapped particles and echoes” or the ‘Magnetic Mir-

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ror System” of Chuan Sheng Liu and Alfred Y. Wong
in Physics Review Letters, Volume 25, page 702, 1970.

A further possible alternative system comprises a
photon echo system in which optical transitions in a
system of atoms are induced by pulses of laser light,
employing the techniques described by N. A. Kurnit, I.
D. Abella and S. R. Hartmann in Physics Review Let-
ters 13, page 567 (1964).

A further possible alternative system may be pro-
vided by a solid state plasma operating in an analogous
manner to the gas plasma system described above.

I claim:

1. A holophone information storing and processing
device comprising generator means for generating
coded signal pulses, representing information, ina form
for causing a systematic disturbance to the motion of
elements within a holophone material, which elements
possess or are caused to acquire a natural periodicity
in their motion, control means for controlling the gen-
erator means, said control means being operative to
cause said generator means to supply to the holophone
material a series of coded signals representing a store
of information and said control means being further op-
erative to cause the generator means subsequently to
supply to the hologram material a series of coded signal
pulses representing a portion of information corre-
sponding to’a portion of said store of information, and
means for detecting subsequent echo waveforms emit-
ted by the holophone material.

2. A holophone information storing and processing
device as claimed in claim 1, wherein the holophone
material comprises a collisionless plasma confined
within a plasma confinement system.

3. A holophone information storing and processing
deyice as claimed in claim 2, wherein the generator
means comprises a matching unit for converting signal
pulses into electrostatic pulses in the plasma, each of
which electrostatic pulses has a spatial periodicity
within the plasma, a stored signal source of coded sig-
nal pulses representing stored information, a cue signal
source of coded signal pulses representing a portion of
information, and means for connecting the stored sig-
nal source and the cue signal to the matching unit to
supply thereto their respective series of signal pulses in
succession.

4. A holophone information storing and processing
device as claimed in claim 1, wherein the holophone
material comprises a material possessing nuclear or
electron spin.

5. A holophone information storing and processing
device as claimed in claim 4, wherein the generator
means comprises a matching unit for converting signal
pulses into radiofrequency electromagnetic pulses, a
stored signal source of coded signal pulses representing
stored information, a cue signal source of coded signal
pulses representing a portion of information, means for
connecting the stored signal source and the cue signal
source to the matching unit to supply thereto their re-
spective series of signal pulses in succession, there
being provided means for applying a fixed external
magnetic field to the holophone material, the fre-
quency of the electromagnetic pulses generated by the
matching unit being close to the nuclear or electron (as
the case may be) spin resonance frequency in the said
external magnetic field.

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6. A holophone information storing and processing
device as claimed in claim 1, wherein the means for de-
tecting subsequent echo waveforms emitted by the
holophone material includes a clarifier for improving
the observed signal to noise ratio.

7. A holophone information storing and processing

s

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device as claimed in claim 6, wherein the clarifier com-
prises means for detecting the signal of the signal out-
put from a monitoring unit, which detects the output

signals from the holophone material.
* OK * * *