US2661442A - Informational storage device - Google Patents

Description

Dec. l, 1953 J. A. BUCKBEE INFORMATIONAL STORAGE DEVICE i Filed March 28, 1950 /A/l/Wro/i JOHN f1. @uc/raft' @f A Alfy Patented Dec. 1, 1953 UNITED STATES PATENT OFFICE INFORMATION AL STORAGE DEVICE John A. Buckbee, Wellesley, Mass., assigner to Raytheon Manufacturing Company, Newton, Mass., a corporation of Delaware Application March 28, 195o, serial No. 152,467

6 o iaims. (o1. 315-12) This invention relates to informational storage devices, and more particularly to an electron discharge device having an electrode Whereon charge patterns may be stored.

In informational storage devices of the type described in greater detail in copending application, Serial No. 66,083, filed December 18, 1948, which hasI matured into Patent No. 2,547,638, issued April 3 1951, entitled Image Storage Tube, a foraminous storage electrode is used which comprises a screen having a conductive side and an insulating dielectric side.

The aforesaid application discloses a structure whereby a single electron gun may be used for both storing the informational charges on the storage electrode and reading informational charges stored thereon. The charges stored on the storage screen by said device were negative with respect to the cathode of the gun.

This invention discloses methods and means whereby a single gun structure may store charges on the storage electrode which are either positive or negative with respect to the cathode of the gun. Briefly, this is accomplished by placing the gun on the conductive side of the storage electrode, placing a repeller electrode on the dielectric side of said storage electrode and spaced therefrom, and positioning an additional grid between and spaced from said repeller electrode and storage electrode. With the conductive portion of the storage electrode maintained somewhat positive with respect to the cathode of the gun, the repeller electrode maintained negative with respect to the cathode of the gun, and the auxiliary screen maintained more positive with respect to the cathode of the gun, electronsr from the gun are caused to pass through the storage electrode and the auxiliary electrode, and, being repelled by the repeller electrode, will strike the dielectric surface of the storage electrode.

By adjustment of the potentials of the various electrodes, the electrons may be made to strike the dielectric surface with a velocity above the critical velocity. As used4 herein, the termv critical velocity is the velocity at which electrons emitted from a surface by secondary emission just equal the electrons initially impinging thereon. Above critical velocity, more electrons are emitted by secondary emission from the surface than initially impinged thereon, while below critical velocity, less electrons are emitted by secondary emission from the surface than initially impinged thereon.

When the electrons impinge on the dielectric surface of the storage electrode at greater than lil critical velocity, the secondary emission electrons are attracted to the auxiliary electrode which is positive with respect to the dielectric surface, thereby causing a net loss of electrons by the dielectric surface and resulting in a positive charge thereon.

In addition, this invention discloses the use of relatively low velocity electrons to read the informational charges stored on the storage electrode. Since these electrons are below critical velocity, they cause little or no secondary emission, with the result that spurious unwanted signals, which could be generated during the readout process by secondary emission electrons, are

eliminated. In addition, since these electrons are below critical Velocity, they either strike the conductive portion of the storage electrode or pass through and are collected by the auxiliary electrode with very few ofl them impinging on thedielectric side of the storage electrode. Asa result, the charge pattern on the storage electrode may be read many times without substantiallyf altering said charge pattern.

Other and further advantages of this invention will be apparent as the description thereof pro-v gresses, reference being had to the accompanying drawing, wherein the single figure illustrates a longitudinal, cross-sectional view of an electron discharge device utilizing this invention and an accompanying circuit illustrating a use of said discharge device.

Referring now to the drawing, there is shown an evacuated envelope IJ having therein adjacent one end thereof a repeller electrode II L, which comprises a flat metallic plate perpendicular to the axis of envelope I0. Adjacent repeller electrode II is an auxiliary electrode I2 comprising a flat mesh screen having a Amesh size, for example, of 400 meshes to the inch. Adv

.jacent screen I2 is a storage electrode I3 comprising a thin flat sheet of metal It having holes punched therein, there being on the order of 4Il0 holes per inch. The side of plate `Ill adjacent electrode I3 is coated with a dielectric insulating material I5 which may be, for example, calcium uoride or a variety of other materials, as set' forth in greater detail in the aforementioned copending application.

Positioned at the other end of the envelope I0 from the electrode structure II through l5 is an electron gun I6 comprising a cathode I1, a control grid I8, a focusing anode I 9,*and an accelerating anode 20, all of any desired construction such as that used in standard cathode ray' tubes.

The grid I8 is connected through a load resistor 2| and a bias battery 22 to the cathode I1 Which is connected to a tap 23 on a battery 24, said tap being denoted, by Way of reference, as zero volts. The focusing anode I9 is connected to a tap 25 on battery 24 having a potential of, for example, 300 volts. A conductive coating covers the inside ofi envelope-,I9 betWeen.-the'areas occupied by the electron'lgun and thezstorage electrode, said coating comprising conductive material, such as finely divided carbon in a binderi The conductive plate I4 of the storage. electrode I3 is connected to a variable tap "26 on'battery 2li which may be adjustedpfor/example, .to affew Volts positive with respect topcathoderI-.

Auxiliary electrode I2 is connected through a load resistor 21 to the movable. arm of athreeposition switch 28, and the repeller electrode II is connected through a load resistor 29 toamovable arm of a three-position switch 30. The movableY arm.` of switch 33 is .gangedto themovable arm oi-switch 2 Thethree positions oiswitches 30. andV 28 may be -designated as ollovvs. Position 1 is usedto Vwrite negative Ycharges .on-the storage electrode, .position .2 is..used to read charges on the storage electrode,.andposition 3- isusedito write .positive .charges-on the storage electrode. .Operation ofthedevicefor each of the .three Apositionsvvill now. be described.

-, YWith the Vswitches 28 4and-33. in position 1, a potential of minusv 100/volts isl applied to the repeller electrode I I and theauxiliary electrode I2. Control .electrode la isnormally biased. to below cutoi bythe .battery 22.. Howeveniin response to a positive input pulse to grid .L8 from -an input gate signal 3l, which may be forexample, a pulse generator, .the electron gun. isy turned. on and theelectron. beaniimpinges upona fportion ofthe electrode structure. The position .is determined by thev beam deflection system in any-wel-I-knownrH manner,l for example, v.as shown.` hereby a set= of deflection coils..32. positioned around the outside of envelope I0. The electrons are irstaccelerated by. passing.. through the focusing.y electrode I9. and the accelerating electrode:2-I.I,.Which is attached toV some suitablehigh potential. source, not .shownfto adequately focus .the beam. The electron. beam passes through the holes in the metallic plate Il:A of the storage electrode I3 with some of the electrons of the beam impinging thereon and being carried off by the-battery 24. The. remaining electrons pass through the storage electrode andare reectedby the -negative potentials on the auxiliary. electrode I2 and the repeller electrode I I.

and impi-nge thereon, thereby buildin-gV up a negative charge on the. storage electrode at. the point of. impingement. It mayfbe noted; that, dueto the negative potential of the repeller electrode4 and auxiliary electrode, electrons.emittedv from the dielectric surface. I5 by secondary emission due to i-mpingement of the initial electrons thereon. will be reattracted to the storage electrode. Thus, a negativecharge` may be stored on. any desired portion ofthe insulator I5 ofv storage electrode I3.

In order to store positive charges Von' theelectrode I3, the switches 28 andA 30 :are placed in position. In. this position, the. repeller electrode is maintained at a negative potential of, for eX- ample; volts, and the auxiliary electrode is maintained at a positive potential of, for example, 200 volts; When thev electron gun I6 is gated on by a pulse from input gate 3l electrons These electrons return to the. dielectric coating. I5 of. the storage .electrode` 4 are beamed toward storage electrode I3 with the major portion thereof passing therethrough and being accelerated toward auxiliary electrode I2. The major portion of the electrons passes through electrode I2 and approaches repeller electrode II which is negative and is repelled thereby. The repelled electrons again pass through electrode I2 and a large: portion thereof s'tr'ilres the dielectric coating I5 of the storage electrode with the remainder passing through the storage electrode I3 and being picked up by the conductive coat- .ing on.theA inner .surface of the envelope IU. The electrons which impinge on dielectric coating I5 'of' electrode I3 are: traveling at greater than cr'ticalcvelocitysand therefore the number of '.fe'lectronsemitted from the dielectric coating I5 vexceeds the number of electrons impinging thereonJ The electrons emitted by secondary emissiorr'from: coating I5 are attracted to auxiliary electrode I2, which is considerably more positive thanthe dielectric. I5, resulting in anetloss' of electrons tothe dielectriccoating I I5; and thereby creating a positive charge on the .portion `ofdielectric I5 upon which the electron beam. impi-nges A lpositive charge .may be built up by this process Vupondielectric coating I5 whichwape proaches aI potential` substantiallyequal to the potential of auxiliary electrode I2'.

In order tov read` informational charges stored onfthe storage electrode I3,. swi-tchesfl" and'i30 are placed in position 2.y In thisposition, :auxiliary electrode I2 is maintained at a potential-of, for example, plus volts, and the reponer-.electrode is maintained atl a potential of, lforiexam-ple, plus 200 volts. When itheelectron IE .isiy turned on, electrons-.travel towardthe storage electrode I3, and a lportion of the electrons im-r pinges on the conductive plate v I4 thereof, .The remaining electrons are either irepel'led: b-y theY negative charge on the dvi-electricY I52and are Icollected by the conductive shield.` on-thefinsidey of envelope III] 4'or pass fthrough rthe storage .electrode I.3-.and are. picked:up by theauxiliary :electrode I2 :01m-the :repeller- Velectrode I I. The number: of electrons which passes through storage electrode I3 is proportional to the charge .on the-dielectric coating thereof and .therefore the .electron Ycurrent `from' electrodes H'v and' I2 isproportional:to4 saidcharge.l This electron current develops a voltage. acrossresistors 21 and-2.9-.. -Sincexthere' is a `large .stray capacitance between electrodes IIy and I2.as.` designatedA by condenser 33,:the re;- sistors 21 and 29 may be considered as aA common load resistor,'and theelectrodes I'Iarid'i lf2 mayo-be consideredasl a .common outputl electrode' for read-outrpurposes it the reading beam; is scanned across the storageelectrodeV I-31ataYrea sonably fast speed, for. example,- scanning; across one horizontalI line of storage electrodeiholesfin ten milliseconds..

This completes the description ofthe particular embodiment of. the invention illustrated hereim- ;bodiment of theinventiondescribe'd herein, ex'- ceptV asdeiinedl by vtheV appended claims.

What is claimed is:

l. An informational. storage device comprising a sourcer of electrons, a. foraminous .storageelec-- trede; means forv beaming electrons from said source to said storage electrode, a repeller electrode positioned on the opposite side of said storage electrode from said electron source, and a grid positioned between said repeller electrode and said storage electrode.

2. An informational storage device comprising a source of electrons, a foraminous storage electrode comprising a grid structure partially coated with insulating material, said insulating material being positioned in the path of electrons directed toward said storage electrode, a repeller electrode positioned on the opposite side of said storage electrode from said electron source, and a grid positioned between said repeller electrode and said storage electrode.

3. An informational storage device comprising a source of electrons, a foraminous storage electrode comprising a grid structure having a conductive side and a dielectric side, said insulating material being positioned in the path of electrons directed toward said storage electrode, a repeller electrode positioned on the opposite side of said storage electrode from said electron source, and a grid positioned between said repeller electrode and said storage electrode.

4. An informational storage device comprising a source of electrons, a foraminous storage e1ectrode, means for producing charge areas on said storage electrode which are positive with respect to said source comprising a repeller electrode positioned on the opposite side of said storage electrode from said electron source, and a grid positioned between said repeller electrode and said storage electrode.

CII

5. An informational storage device comprising a source of electrons, a foraminous storage electrode having a conductive side and a dielectric side, and means for producing charge areas on said storage electrode which are positive with respect to said source comprising a plurality of electrodes positioned on the dielectric side of said storage electrode.

6. An informational storage device comprising a source of electrons, a oraminous storage electrede having a conductive side and a dielectric side, means for producing charge areas on said storage electrode which are positive with respect to said source comprising a plurality of electrodes positioned on the dielectric side of said storage electrode, and means for causing electrons from said source to impinge on said dielectric side with greater than critical velocity.

JOHN A. BUCKBEE.

References Cited in the le of this patent UNITED STATES PATENTS Number Name Date 2,280,191 Hergenrother i- Apr. 21, 1942 2,291,577 Farnsworth July 28, 1942 2,454,410 Snyder, Jr. Nov. 23, 1948 2,460,093 Law Jan. 25, 1949 2,470,875 Snyder, Jr. May 24, 1949 2,481,458 Wertz Sept. 6, 1949 2,503,949 Jensen et al. Apr. 11, 1950 2,538,836 Jensen 1 Jan. 23, 1951 2,547,638 Gardner Apr. 3, 1951

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