US2794937A - Electronic information-storing devices - Google Patents

Description

June 4, 1957 F. c. WILLIAMS ETAL ELECTRONIC INFORMATION-STORING DEVICES .2 Sheets-Sheet 1 Filed Nov. 7, 1950 2 G N o L A E m m M a 3 uum zu+ 5 j 4 .C IHHQHU a A. .2 oHHH 1 m- DOT DASH V BEAM DEFLECTION X- SCAN June 4, 1957 2 Sheets-Sheet 2 Filed Nov. 7, 1950 P M VA 2 a N h ML AF EE 3 BD A C a HM S L A we P 8 a m T m HN. E O T E A MG G D I'IITN v 3 CE 6 5 R M/DG 2 n United States Patent 2. 94.931, ErEcTRoNlc INFORMATIQN-STQRKNG DEVICES.

Frederic. CallandLWilliams,,.Timperiey,, and, ram. Kilbum,

Davyhulnie, Manchester EiIgliand 'Qassignors to National Research Development Corporation, London,

Thisinvention relates, to, a method of andmeans for storing information. ofthe kindemploying a cathode ray tube, haying. an insulating screen, a positive. charge being generated at a selected region of the screen surface, owing to the'liberation, ofsecondary electrons. from the region by ,thecathode ray beanrcin order to record one item: of

information, and a second. item of information being recorded. when. required. by subsequently reducing the positive,,charge at the. region by. the furtherliberation of secondary electrons. to the region.

Examples of methodsof this kind are described, for

instance,,in.U. ,S.. patent. appln..Serial..No. 165,622, filed June 2, 1950, which has been. abandoned; in favorof. the continuationthereof, application; Serial. No. 353,819, filed May 8, 1953, byFredericl 3..Williams. et. al-., now U. S Patent 2,709,230ggantedlMay 2 7, 19.55.

Thefpresentinventionl hasf for its. object to provide a new or. improved, method and means. of the. kindset forth.

'According to the present. invention. there is provided apparatus comprising means for deflecting thebeani at the said region in. order to generatea positivecharge along, a. strip. of the screen, means for ,directin gthe beam to bombard. a spot on therscreen on or, near the strip in order to reduce the positive charge onthe strip by the release. of secondary emission thereto, and, control means forcausing or. permitting the bombardment of said spotor preventing such bombardment. according to'the nature of the information to be stored.

The present invention alsoprovides, a method. of storing; information comprising directing the cathode ray beam recnrrentlyupon a, region of the screen,,intensifying said beam when. directed upon said. region, deflecting the intensified bearn over a; strip upon said screen: totgenerate a positive charge on said. strip and thereby recordone kind of information, when required to record a second kind of information subsequently intensifying said beam upon a spot of the screen to liberate. secondary electrons to reduce said positive charge, and. applying. signals. generated on a pick-up'plate. associated with the screen, and corresponding to changes. in the charge upon the screen, to control the intensification of saidbeam to regenerate thel ch'arge. upon said strip. V

The speed of deflection along the strip is made slow enough to ensure that the creation of the positive, charge is complete but fast enough to ensure that there is no substantial reduction of the positive charge set up at the first part of the strip scanned, by the secondary electrons liberated during the scanning and falling on the part of the strip previously scanned. The speed of scanning will depend on the particular operating conditions of the cathode ray tube. The question of Scanning speeds is discussed at length in a paper entitled A storage system for use with binary-digital computing machines. in the Proceedings of. the Institution of Electrical Engineers, part. III, No, 40, March 1949, pp. 81-100.

The scanned strip may conveniently be substantially straight.

'ice

The .inventionwill now be described with reference to the accompanying drawings; in which:

Figures; 1 and 2 are diagrams illustrating thepnnciple of the invention,

Figure 3 shows waveforms of potentials that may be used for carrying the invention into effect, and

Figure 4 is a block; circuit diagram of one embodiment of the invention,

In Figure 1, 2 represents a strip on the insulating S111.- face of a screen of a storage tube scanned by an electron beam to leave a trough of positive charge as indicated by the graph ofFigure- 2 at 3; This charge; may be left unmodified land may then represent, say, the digit 0.

At 4 in Figure 1 there is represented a strip which is first scanned to leave a trough of positive charge, as in the case of the stripZ, and is. then irradiated at a spot 5 to, liberate more secondary electrons which wholly or partially fill up the trough of positive charge along the strip 4, except, of course, lat the spot 5. The resulting charge is indicated in Figure 2 by the graph at 6, the dotted line 7 indicating the positive charge before it wasreduced by the further liberation of secondary electrons from thespot 5; This modified form of charge distribution may then represent the digit 1. The secondary electron'swhichreduce the positive charge on the maybe'liberated from a. spot outside the stripso longasthespot is close' enough for the neutralislaltion of charge to take place.

One embodiment of the invention will now be described with reference toFigures 3- and 4.

In Figure 4; a cathode raytube 10 has upon an end wall the usual screen ll of phosphor. A pulse generator 20* generates pulses to control and synchronise the generation of the various waveforms required for operating the circuit. Thus after frequency division at 21 the pulses contro'l X and Y-sc-an generators 22 and- 23 which may generate and apply to deflectingmeans 17 and 18 respectively such waveforms as will cause the cathode ray. beam to. scan a raster onthe screen 11: the X-scan waveform is preferably paused as shownin Figure. 3 (f) the beam thus moving in a series of slteps and pausing betweenthe steps.

Pulses from 20 also control the generation by a dot generator 24. of a-waveform in Figure 3(a) and by a dash generator 26 generating a positive-going pulse over the recurrent time interval t to t,. A meditation pulse generator 32 generates negative/going pulses in the recurrent interval z to 1 and these pulses combinedwith those of Figure 3(a) give rise to Ithe dash waveform of Figure 3(b). The pulses from 24, 26, 32 and from a strobe pulse generator 28 are applied to a gate circuit which operates in a manner more fully described in the specification of U. S. pat. appln. Serial No. 165,262, filed May 31, 1950. Briefly the dot waveform of Figure 3(a) is normally applied to the grid 13 of the tube 10 from the gate 25 land may represent the quantity 0. When it is desired to record the quantity 1, a suitable write voltage is appli'ed at 29 to open the gate 25 to the passage of a dash pulse from the generator 26. and the waveform applied to the grid 13 is then changed to the dash and meditation waveform of Figure 3(b). The dot and dash waveform generators 24 and 26' constitute switching means since they generate pulses which determine the times at which the beam is. switched on and off.

The gate 25 is also controlled by voltages from a pick-up plate 19 upon the outside of the wall of the tube 10 and electrostatically coupled to the screen 11. These voltages afteramplification at 27 and strobing by pulses from 28 are arranged to be of one polarity or the other according as the beam is switched on to bombard a spot on the screen which bears a charge as in Figure 2 at 3 or 6. and .thepolarityis arranged to determine whether, in,

plaltes 18.

the absence of signals applied at 29, the waveform applied to 13 shall be the dot or the dash waveform. In this way, as fully explained on the earlier specification, the charge on the screen 11 can be regenerated in the absence of signals applied at 29 and changed when required by signals applied at 29. Such signals may for example be received from a computor to which read signals are applied from a terminal 30, the latter signals representing the stored information. The gate 25 constitutes a selecting means responsive to a write voltage applied at 29 or to a voltage applied thereto from the pickup plate 19 to select the dash waveform for application to the beam intensity control electrode 13. I

In addition to the beam deflections already described,

means which may be separate from but are conveniently associated with the normal scanning means 17, 18, 22, 23, are provided for deflecting the beam while it is turned on during the interval t to t A waveform suitable for effecting this deflection is shown in Figure 3(a) and it may be generated by a circuit 33, combined with the Y scan voltage from 23 and applied to the Y deflecting It is, however, not necessary that the deflection should be in the Y direction but it is preferably at an angle to the X direction. The waveform of Figure 3(c) may be produced by the addition of a saw-tooth wave as in Figure 3(d) and an amplitude-limited pulse as shown in Figure 3(e). 7 When the dot Waveform is applied from the generator 24 to the grid 13 in Figure 4 the beam is switched on only from t to 1 (and at corresponding later times) and during this time the beam is deflected by the voltage of Figure 3(c) at right angles to the X direction whilst the beam is stationary in the X direction. The conditions are, therefore, as indicated at 2 in Figure 1 and 3 in Figure 2.

When the dash waveform is applied from the generator 26 to the grid 13, the same conditions as with a dot are first produced and then, while the beam is still held stationary in the X direction, it is switched on from t, to t thus producing the conditions represented in Figure 2 at 6.

When the beam is next switched on upon a region charged as at 3 in Figure 2 it may be arranged to generate in the plate 19 a negative pulse, during the strobe interval determined by the pulses from 28. When the beam is next switched on upon a region charged as at 6 in Figure 2 it will generate a positive pulse. These pulses, amplified at 27, are applied to the gate 25 and control regeneration as already described.

The slope of the deflecting wave of Figure 3 (0) during Ithe time I to t, is made such that the beam is deflected fast enough to prevent any considerable neutralisation of the positive charge behind the beam.

We claim:

1. A method of storing information in which a cathode ray beam is caused to strike a surface of an insulator and to produce a positive charge on such surface by the liberation of secondary electrons, the method comprising storing one kind of information by sweeping the beam along a strip of the surface to produce a positive charge along the strip and, when required, converting the said positive charge to another ch arge condition representative of a second kind of information by bombarding with the cathode ray beam a spot on the surface on or near the strip from which spot secondary electrons pass to the strip and reduce the positive charge thereon.

2. A method according to claim 1, wherein the said sweeping of Ithe beam is at a speed high enough to prevent substantial reduction, by secondary emission, of the positive charge behind the beam.

3. A method of storing inforamtion and of regenerating the store employing a cathode ray tube having an insulating screen and a pick-up plate electrostaltioally coupled to said screen, said method comprising directing :the cathode ray beam recurrently upon a region of the screen, intensifying said beam when directed upon said region, deflecting the intensified beam over a strip upon said screen to generate Ia positive charge on said strip and thereby record one kind of information, when required to record a second kind of information subsequently intensifying said beam upon a spot of the screen to liberate secondary electrons to reduce said positive charge, and applying signals generated on said pick-up plate to control the intensification of said beam to regencrate the charge upon said strip.

4. Apparatus for storing information comprising a cathode ray tube, an electric charge-retaining surface within said tube, electron beam producing means including beam intensity control means in said tube, means to sweep the beam recurrently along a track upon said surface, means coupled to said beam intensity control means to intensify the beam for short periods at predetermined regions along said track to produce positively charged ships on said screen, means coupled to said beam intensity control means to re-intensify the beam at spots upon said screen to liberate secondary electrons to reduce said positive charge at said regions, gating means to control the operation of said re-intensifying means to regulate said re-intensification, and means to apply information to be stored to said gating means.

' 5. Apparatus according to claim 4, comprising means to deflect said beam at each of said regions at an angle to said track, whereby said strips are at an angle to said track.

6. Apparatus according to claim 5, wherein said angle 'is approximately a right angle.

7. Apparatus according to claim 4Qcomprising a pickup plate electrostatioally coupled to said screen and means to apply signals generated on said plate, according to their nature, to said gating means to permit and prevent saidre-intensification and .thereby regenerate the appropriate charge upon said region.

8. Apparatus for storing information comprising an electric charge-retaining surface, a source of electrons, means accelerating electrons in a beam from said source toward said surface, deflecting means adjacent said beam causing said beam to scan said surface in a raster of substantially parallel lines and deflection control means coupled to said deflecting means and causing said beam to sweep said surface in a purality of strips at a predetermined angle to said substantially parallel lines during the beam scanning over each of said lines, includingbeam intensity control means, first signal means coupled to said intensity control means and causing said screen to be bombarded along one of said plurality of angular strips when a first information is to be stored, and second signal means coupled to said intensity control means, said second means causing said screen to be bombarded along one of said plurality of angular strips followed by a further bombardment in the region of said strip when a second information is to be stored, each of said first and second signal means being coupled to said intensity control means through a gate circuit, a pick-up plate adjacent said storage surface and coupled to said gate circuit, the signals in said pick-up plate causing said gate circuit to selectively pass signals from said first and second signal means to regenerate information upon said storage surface.

9. The apparatus of claim 8 in whichsaid deflecting means includes a generator of voltage of stepped waveform which causes each of said substantially parallel lines to be scanned in an intermittent motion of starts and stops, said deflection control means being operative to effect said angular sweep during each of said stops in scanning.

10. Apparatus for storing information comprising a cathode ray tube, an electric charge-retaining surface Within said tube, means for deflecting the cathode ray beam of said tube, means for controlling the intensity of said beam, a first electric generator generating an approximately sawtooth waveform extending between upper and lower limiting values, means to apply said waveform to said deflecting means, means for generating two switching waveforms for application to said beam intensity controlling means, one of said switching waveforms causing the beam to be switched on during one excursion of said sawtooth waveform between said limiting values and then to be switched off, and the other of said switching waveforms causing the beam to be switched on during one excursion of said saw-tooth waveform between said limiting values and also, subsequently, when said sawtooth waveform is at a value between said upper and lower limiting values, and selecting means responsive to the information to be stored to apply said switching waveform selectively to said beam intensity control means according to the information to be stored.

11. Apparatus according to claim 10, including a pickup plate capacitively coupled to said surface and means for applying signals from said pick-up plate to said selecting means to select the one of said waveforms to be applied to said beam intensity control means.

12. Apparatus for storing information comprising an electric charge-retaining surface, a source of electrons, means accelerating electrons from said source in a beam towards said surface, first deflecting means for deflecting said beam in a first direction, a scanning oscillation generator to generate a stepped waveform comprising a series of steps of different, substantially constant values, means to apply said waveform to said deflecting means to deflect said beam in said direction in steps between which the beam is substantially stationary, second deflecting means for deflecting said beam in a second direction at a predetermined angle to said first direction, a second oscillation generator generating a second deflecting waveform having varying portions separated by portions of substantially constant value, said varying portions occurring during said steps of substantially constant values respectively, and means to apply said second deflecting waveform to said second deflecting means.

13. Apparatus according to claim 12, including gating means, a first beam switching means coupled to said gating means and causing said surface to be bombarded substantially only during said varying portions of the second deflecting waveform when a first information is to be stored, and second beam switching means coupled to said gating means and causing said surface to be bom barded during said varying portions and during at least a part of the next succeeding portion of substantially constant value in said second deflecting waveform when a second information is to be stored.

14. Apparatus according to claim 12, including selecting means, first control means coupled to said selecting means and when operative causing said surface to be bombarded substantially only during said varying portions of the second deflecting waveform, and second control means coupled to said selecting means and when operative causing said surface to be bombarded during said varying portions and during at least a part of the next succeeding portion of substantially constant value in said second deflecting waveform, said selecting means eing responsive to information to be stored to select the one of said first and second control means which is made operative.

15. Apparatus according to claim 14, including a pickup plate capacitively coupled to said surface and means for applying signals generated in said pickup plate to said selecting means to select the one of said first and second control means which is made operative.

References Cited in the file of this patent UNITED STATES PATENTS 2,178,074 Jakel et al. Oct. 31, 1939 2,461,667 Sunstein Feb. 15, 1949 2,548,789 Hergenrother Apr. 10, 1951 2,639,425 Russell et al. May 19, 1953 2,660,669 West Nov. 24, 1953

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