US2728872A

US2728872A - Direct-viewing storage tube with character writing electron gun

Info

Publication number: US2728872A
Application number: US387984A
Authority: US
Inventors: Henry M Smith
Original assignee: Hughes Aircraft Co
Current assignee: Raytheon Co
Priority date: 1953-10-23
Filing date: 1953-10-23
Publication date: 1955-12-27
Anticipated expiration: 1972-12-27
Also published as: GB770333A

Description

2 Sheets-Sheet l H. M. SMITH DIRECT-VIEWING STORAGE TUBE WITH CHARACTER WRITING ELECTRON GUN Dec. 27, 1955 Filed oct. 23, 1953 ii lllll F11.

Dec. 27. 1955 H. M. SMITH 2,728,872

DIRECTVIEWING STORAGE TUBE WITH CHARACTER WRITING ELECTRON GUN Filed oct. 25, 1953 2 sheets-sheet 2 [h @um Q E A uw uns in@ Slm @l BY 4MM, W

DmECT-VIEWHNG STGRAGE TUBE WITH CHAR- ACTER WRITNG ELECTRON GUN Henry M. Smith, Pacific Palisades, Calif., assigner, by

mesne assignments, to Hughes Aircraft Company, a corporation of Delaware Application ctober 23, 1953, Serial No. 387,984

7 Claims. (Cl. S15- 12) This invention relates to direct-viewing storage tubes and more particularly to a direct-viewing storage tube incorporating apparatus for producing an electron beam with a cross sectional area having the configuration of a desired information character for writing the character directly on the storage surface of the tube in a single operation.

The storage tube of the present invention comprises means for producing a character writing electron beam, a gun for producing flood electrons, a viewing screen, and a foraminous storage screen disposed adjacent to the viewing screen to control the flow of ilood electrons to the storage screen. The character writing electron beam is produced by means which include a matrix mask of all the information characters that it is desired to reproduce. Further, an electron gun for producing an electron beam of sufficient cross sectional area to cover one character of the matrix mask. Deilecting means are utilized to direct this electron beam through the aperture of the matrix mask having the configuration of the character that it is desired to reproduce. In this manner, certain electrons in the beam are intercepted so that the remaining cross section of the beam has the shape of the desired character.

This electron beam is then directed by means of an electrostatic lens and deflecting means to the portion of the storage screen in register with the position on the viewing screen where it is desired to reproduce the character. The high energy electrons of the beam produce a positive charge on the bombarded areas of the storage screen, which allows the ood electrons to pass through to the viewing screen to produce a continuous visual reproduction of the character thereon.

The character writing electron beam of the disclosed tube constitutes a partially intercepted beam which has a cross section conforming to the conguration of the area of the character being reproduced. This results in an electron beam of relatively low density, making a storage screen with a fast writing speed desirable. A storage screen having this feature is incorporated in the tube of the present invention, and is described in a copending application for patent Serial No. 299,363, entitled Method and Apparatus for Utilizing Electron Bombardment Induced Surface Conductivity, by Siegfried Hansen, tiled July l5, 1952. A storage screen of this type comprises a contrast control grid with a layer of dielectric material disposed thereon, and a collector grid in contact with the dielectric material wherein a storage surface is provided by the exposed surface of dielectric material. A potential gradient is maintained from the storage surface to the collector grid to effect charging of the storage surface by a means believed to be by electron bombardment induced conductivity. That is, when an area of the storage surface is bombarded by high energy electrons, a large number of electrons in the dielectric material are liberated from their molecular bonds and are attracted through the molecular matrix constituting the dielectric material to the collector grid by the potential gradient to produce a positive charge on the storage surface.` In this manner, a writing speed ld States Patent ice is realized that is several times faster than possible with conventional secondary electron emission storage screens.

Apparatus capable of producing an electron beam having a cross section in the form of a desired character together with means for selecting dilferent characters is well known in the art. This apparatus, however, has normally been used in conventional cathode ray tubes with the resulting concomitant limitations. For example, if it is desired to read information directly from the viewingscreen of the tube, it would be necessary to repeatedly excite the screen with the same information in order to obtain the persistence required. Also, if a photographic record were to be made, the sequential producing of each character with limited persistence would make it necessary for the lens of the camera to remain open during the entire writing process. This long exposure would require that all extraneous sources of light be eliminated.

The tube of the present invention, on the other hand, has none of these limitations. Information, once written on the screen of the storage tube remains until removed. Thus, a photographic record of all the information on the viewing screen may be made with a single short exposure and information could be read from the screen without successively exciting the screen with the same information. In addition to these advantages, the storage screen of the aforementioned type is capable of very fast writing speeds, making it particularly adaptable for use with the character writing electron beam which inherently has a comparatively low electron density.

It is therefore an object of this invention to provide a cathode ray device for producing a sequence of visual characters for desired intervals of time, each character being produced by means of a discrete operation with an electron beam.

Another object of this invention is to provide a directviewing storage tube incorporating apparatus for producing a character writing electron beam.

Still another object of this invention is to provide a cathode ray tube device including a storage screen capable of fast writing speeds, together with apparatus for producing a character writing electron beam.

A further object of this invention is to provide a directviewing storage tube with apparatus for producing a character writing electron beam comprising a matrix mask and an electrostatic lens for focusing the matrix mask on the storage screen of the tube.

A still further object of this invention is to provide a direct-viewing storage tube with apparatus for producing a character writing electron beam comprising a matrix mask and apparatus for directing the electron beam to a desired portion on the storage screen including an electrostatic lens for focusing the matrix mask on the storage screen whereby successive paths of the electron beam cross. through a common line, and electron beam dellecting means having a center of deflection on said line.

The novel features which are believed to be characteristic of the invention, both as to its organization and method of operation, together with further objects and advantages thereof, will be better understood from the following description considered in connection with the accompanying drawings in which an embodiment of the invention is illustrated by way of example. lt is to be expressly understood, however, that the drawings are for the purpose of illustration and description only, and are not intended as a definition of the limits of the invention.

Fig. l illustrates a sectional view of an embodiment of the disclosed tube;

Fig. 2 illustrates a plan view of the matrix mask in the apparatus for producing the character writing electron beam;

Fig. 3 is a plan view of the storage screen in the tube of Fig. l; and

Fig. 4 is a schematic diagram on the operation of the lens system of the tube of Fig. 1.

Referring to Fig. l, there; is shown an embodiment of the present invention comprising an evacuated envelope 10' which in its enlarged right portion, asviewed in the figure, is a storage screen 12` and ae viewing screen 14. Facing the storage screen 12 in the left portion of envelope 10' as viewed in the gure', is a flood gun 16 and apparatus for producing a character writing electron beam and directing it in a desired direction towards storage screen 12. This apparatus comprises an electron gun :i8 for generating an electron beam, a matrix mask 20 having apertures in the shape of the characters to be reproduced, and selection meansv 22. for directing the electron beam through the aperture corresponding to the character to be reproduced. Subsequent to penetrating an aperture of the matrix mask 20,. the electron. beam traverses an electrostatic lens 24 and deflecting means 26 for directing it in the desired direction towards storage screen t2. Although a magnetic lens may be employed' inlieu of electrostatic lens 24, the electrostatic lens is preferred in that it does not rotate the electron beam.

Electron gun 1S, which. produces the initial writing beam of electrons, comprises a cathode 3b with a heating clement .32, an intensity grid 34, accelerating electrodes 36, 38 and a focusing electrode 37. Heating element 32, one side of which may be connected to cathode 30 as shown, is connected across. a source of potential such as a battery 40. Cathode 30 is maintained at a potential of the order ot -3000 volts with respect to ground by means of a connection to the negative terminal of a battery 42, the positive terminal of which is connected to ground. intensity grid 34 is maintained at a suiciently negative quiescent potential with respect to that of the cathode 39 so that the flow of stream electrons is entirely cut oft. This is accomplished by a battery 43, providing a potential of the order of 2000 Volts in series with a resistor d4 connected between cathode 30 and grid 34.

When it is desired to cause the electron stream to flow, the potential of intensity grid 34- is increased until it is only from 50 to 100 volts` negative relative to the potential oi cathode 36. In the present case, this is accomplished by impressing a pulse of suitable amplitude generated by a pulse generator 45 on intensity grid 34 by means of a connectionA thereto from pulse generator 4S through a capacitor 31. The duration of the pulse is for the time necessary to Write one character on the storage screen i2,

Electrodes 36, 37 andy 38 form an electrostatic lens system for focusing the electron beam. Electrodes 36, 3S are maintained at apotential of the order of 200 volts positive with respect to ground by means, of a connection to a reference bus 39 which is maintained at the desired potential by suitable connections to a battery 41. An adjustable potential of the. order of +800 volts relative to cathode 30 or -2200 volts with respect to ground is maintained on electrode 37 for focusing the electron beam. ri`his is accomplished by means of a connection fromy the electrode 37 to an adjustable tap 46 of a potentiometer 4"/ whichl is, in turn, connected across battery 42.

Selection means 22, for directing the electron stream through thc aperture corresponding to the character in matrix mask 20 to be reproduced, comprises vertical selection plates 43 and horizontal selection plates 49. Vertical and horizontal selection plates' 4d, 49 are maintained at a quiescent potential of +200 volts with respect to ground by means of a connection to reference bus 39 through isolation resistors t), 51' and 52, 53, respectively. Vertical selection plates 45 are energized by a vertical voltage generator 55 connected across isolation resistors Sti, 51. Similarly,.horizontal. selection plates 49 are energized by a horizontal voltage generator 54 connected across isolation resistors 52, 53'. A` control circuit 56, coupled to pulse generator 45 and generators 54, 55, is

provided to first determine the vertical and horizontal voltages to be produced by generators 54, 55 in order to have selection means 22 direct the electron beam through the aperture corresponding to a desired character in matrix 29 and, secondly, to trigger pulse generator 45 to cause the electron stream to flow through the aperture for a period of time required for the character to be written on the storage screen 12. It is preferred that there be no ilow of beam electrons when changing from one aperture to another in the matrix 20 and further, that the electron beam does not dow for too long a period of time through a single aperture because of the possibility of damage to the storage screen 12.

The matrix mask 20, a plan view of which is shown in Fig. 2, comprises a thin conductive electrode having an aperture in the shape of each character that it is desired to produce. Although the arrangement of the characters is entirely arbitrary, it is preferable that the most used characters be disposed in the center region of the mask 20 in order that minimum deflection of the electron beam be required to direct it through the apertures of those most used characters. The electron beam, of course, must be of appropriate cross sectional area so as to completely cover only one aperture in the matrix at any one time. illustrated in Fig. 2 is the matrix mask 20 with forty-five apertures shown by way of example. In the arrangement of characters shown, an E is disposed in the center position where an undeected electron beam would strike. The remaining characters are disposed at equal increments of horizontal and vertical deflection away from the E, as shown.

Disposed about the path of the electron beam after it has penetrated through an aperture in the matrix mask 20 are the electrostatic lens 24 and electron beam dellecting means 26. Lens 24 comprises

annular electrodes

59, 60 and 61, which are all of the same diameter and disposed as shown in the ligure. Electrodes 59 and 61 are maintained at the potential of 200 volts positive with respect to ground by means of a connection to reference bus 39, while electrode 60 is maintained at an adjustable potential of the order of +1000 volts with respect to ground. This latter potential is impressed on electrode 6i) by means of a connectionto an adjustable contact 64 of a potentiometer 65 which is, in turn, connected across a battery 66 which has its negative terminal connected to ground. The function of lens 24 is to bring the matrix 2t) into focus at the storage screen 12 in such a manner that the electron beam always crosses over at the centers of deection of electron beam deflecting means 26. That is, the various paths of the electron beam, subsequent to passing through the apertures of matrix 20, would cross over at the centers of deflection of deecting means 26. .it is apparent that the magnetic focusing, may also. be used to focus the matrix mask Ztl on the storage screen l2, and is considered to be within the scope of the present invention. A magnetic lens, however, as compared to the electrostatic lens 24 used in this application, has the disadvantage of causing the electron beam to rotate. In a comparatively strong magnetic eld, individual characters may even be distorted due to some portions rotating more than others.

The electron beam deliecting means 26 comprise horizontal. deiiection plates 68 and vertical deflection plates 70 disposed about the path of the electron beam, as shown. Horizontal and vertical deflection plates 68, 70 are maintained at a quiescent potential of 200 volts positive with respect to ground by means of connections to reference bus 39 through

isolation resistors

72, 73 and 74, 75, respectively. Horizontal. deflection plates 68 are energized by a horizontal deliection voltage generator 76 connected thereto across

isolation resistors

72, 73 through capacitors 77, 78. Similarly, vertical deflection plates 70 are energized by a vertical dellection voltage generator Si) connectedl thereto across

isolation resistors

74, 75 through capacitors 81,82.

Flood gun 16', in conjunction with electrodes 95 and 96,

amasar;-

produces a broad beam of flood electrons that is directed uniformly over the entire area of storage screen 12. Flood gun 16 is disposed adjacent to one of the vertical deflection plates 70, and comprises a cathode 90 surrounded by an intensity grid 91 having a circular aperture in its center portion and

annular electrodes

92 and 93 disposed in succession in front of and concentrically about the aperture in intensity grid 91. The cathode 90 is operated at ground potential by means of a connection thereto while intensity grid 91 is maintained at a potential of the order of 100 volts negative with respect to ground. The latter is accomplished by means of a connection from intensity grid 91 to an adjustable tap 97 of a potentiometer 98, which is connected across a battery 100, an intermediate point of which is connected to ground so that both positive and negative potentials are available from potentiometer 93. Electrode 93 is maintained at a potential of the order of +200 volts with respect to ground by means of a connection to reference bus 39 while electrode 92 is maintained at a potential of from 150 to 200 volts positive with respect to ground, depending upon the desired diameter of the beam of ilood electrons. This potential is applied to electrode 92 by means of a connection thereto from a tap 99 of potentiometer 98.

Electrodes 95 and 96 are disposed concentrically about the inner periphery of envelope 10 in succession from vertical deilection plates 70 to storage screen 12. These electrodes 95, 96 are composed of a conductive coating, which may be provided, for example, by painting the envelope 10 with a colloidal solution of carbon such as Aquadag Electrode 95 is maintained at a potential of the order of +200 volts with respect to ground by means of a connection to reference bus 39. Electrode 96 is maintained at a potential of from 50 to 100 volts positive with respect to ground by means of a connection to an adjustable tap 103 of a potentiometer 105 which is connected across a battery 106, an intermediate terminal of which is connected to ground.

Disposed in the enlarged portion of envelope 10 opposite to the ood gun 16 and the apparatus for producing the character writing electron beam are the storage screen 12 and the viewing screen 14. Fig. l illustrates an enlarged cross sectional view of the storage screen 12 which is disposed adjacent to and in front of the viewing screen 14 so that it may control the ow of flood electrons thereto. Storage screen 12 comprises a screen grid 110 which serves as a contrast control grid, a thin at screen 112 with an annular electrode 113 about its periphery to provide a collector grid, and a dielectricmaterial 114 disposed between contrast control grid 110 and the ilat screen 112 whereby the exposed portions of the surface of the dielectric material 114 provide a storage surface. In accordance with the tentative theory of operation of the device, the dielectric material 114 used for this purpose must exhibit induced conductivity and secondary electron emission characteristics when bombarded by electrons. An enlarged view of a portion of storage screen 12 showing the contrast control grid 110, flat screen 112, and dielectric material 114, is illustrated in Fig. 3. As shown in this figure, one set of the parallel Wires constituting iiat screen 112 is disposed at an angle of approximately 27.5 degrees relative to the sides of the rectangular openings of grid 110 in order to avoid the formation of a moire pattern by the iiood electrons in passing through storage screen 12.

A suitable material for contrast control grid 110, is, for example, an electroformed 40 percent transparent nickel screen having 250 openings per inch. The number of openings per inch, and other dimensions of the screen used for making contrast control grid 110 is not especially critical, the primary consideration determining the above parameters being the ultimate transparency of the screen to electrons,.the eld penetration required, and the ultimate definition desired. The contrast control grid 110 is supported by a metal frame 116 which also serves as a mechanical support for the remaining elements of storage? screen 12.

Applied directly on the contrast control grid is dielectric material 114 which provides the storage surface. Dielectric material 114 must have a very high specic resistance and, as previously mentioned, must exhibit induced conductivity and secondary electron emission when subjected to bombardment by high energy incident electrons. The property of induced conductivity of a normally nonconducting dielectric material is brought about because of the matrix structure of solid material. The molecules composing the material form a matrix structure which occupies only a small fraction of its apparent volume. When bombarded by high energy electrons, large numbers of electrons are freed from their molecular bonds to constitute electrons raised to the conduction band energy level. These freed electrons are then attracted through the molecular matrix of the material for a distance of the order of a fraction of a millimeter by means of a suitable potential gradient. A representative material that may be used for dielectric material 114 is, for example, talc.

Mounted in contact with the exposed surface of dielectric material 114 is the ilat screen 112 which constitutes a thin flat metallic screen. This screen may be of an appropriate conducting material such as an evaporated aluminum, silver or gold mesh, having a thickness of the order of l0 to 30 millionths of an inch, a pitch of 0.010 inch and a hole size of 0.008 inch by 0.008 inch. The exposed surface of the dielectric material 114 within the holes of flat screen 112 constitutes the storage surface of the storage screen 12.

Contrast control grid 110 is maintained at an appropriate potential so as to regulate the ow of ood electrons through storage screen 12 to viewing screen 14. This potential may be of the order of -10 volts with respect to ground, and is applied by means of a connection to an adjustable tap 104 of potentiometer 105. Flat screen 112 is maintained at a potential of the order of 175 volts with respect to ground by means of a connection to a tap 102 of potentiometer 105.

Viewing screen 14 is disposed adjacent to and behind` storage screen 12 with respect to the electron beams. This screen is disposed on the inner surface at the end of the enlarged portion of envelope 10, and comprises a conductive transparent layer and a thin fluorescent screen 122. Conductive transparent layer 120 is disposed directly on the glass surface, and may be provided by a layer of stannous oxide. One method of forming this layer of stannous oxide on the glass is to expose it to the action of stannous chloride in the presence of oxygen. Various other viewing screen materials may be used, depending on the desired characteristics. The construction of such viewing screen, however, is not critical for the purposes of this invention. Conductive layer 120 is maintained at a high positive potential so as to acceleratek electrons passing through the interstices of storage screen 12 to a suiiiciently high velocity so that their kinetic energy will be converted to a desired amount of light at the time of impingement upon the viewing screen. This potential is applied by means of a connection to the positive terminal of a battery 124, the negative terminal of which is connected to ground. The magnitude of the potential provided by battery 124 may be of the order of from +5000 to -{-l0,000 volts.

In the operation of the character writing direct-viewing storage tube of the present invention, the horizontal and vertical Voltage generators 54, 55, in response to control circuit 56, produce appropriate voltages which are impressed on

selection plates

48, 49 for directing the path of the electron beam towards the aperture corresponding to the character in matrix mask 20 that it is desired to write. The voltage applied to electrode 37 of the lens system provided by

electrodes

36, 37 and 38, is adjusted by means of tap 46 of potentiometer 47 so that the electron beam has a cross sectional area at the matrix mask 20 to cover only one complete character. Upon passing through the matrix mask 20, beam electrons not directed through' the aperture of the character to be written, are interceptedso that an electron beam is produced having a cross sectional area with the shape of the character.

After passing through the matrix mask 2i), the electron beam is directed to a predetermined portion or" the storage .screenI 12 by meansot the electrostatic lens 24 and electron beam deilecting means 26. In order to explain more clearly the preferred manner in which this effected, reference is made to Fig. 4. This ligure shows a schematic diagram of the matrix mask 2li, electrostatic lens 24 including electrodes S9, 6l! and 6i, vertical dcection plates 70 andy storage screen l2. Further, dashed lines 139 indicate equipotential surfaces of the electrostatic lens 24 and lines 132 represent successive paths of the electron beam when acted upon by the lens only. The electrostatic lens 24k is preferably adjusted to focus the matrix mask 20 on theV storage screen l2 in such manner that successive paths 132 of the electron beam cross over at a common point 134 in the plane shown. lt is to be notedV that the velocity of the electron beam may be increased after it has passed through the matrix mask 20, if desired, in order. tominimize the divergence of the successive paths 132 of the electron beam and thus aid in focusing the matrix mask 2G on the storage screen i2. This would also reduce the velocity at which the electrons are incident on the mask Ztl, thus considerably reducing the energy dissipated about the` edges of the apertures.

As shown in Fig. 4, the common point 13d is a distance a from the lens, and a distance b from the storage screen I2. With this being the case, the apertures of matrix 2b, focused on the storage screen l2, are magnified by an' amount I'n order to greatly simplify the directing of the electronr beam to predetermined portions of the storage screen 12, the common point i3d should coincide with the center of deection of the vertical deflection plates 7l). In this event, compensating voltages that are directly proportional' to the deilecting potentials impressed on the deflecting plates d3 of selection means 22 may be applied to deflection plates 7i) so that the beam may be directed to a predetermined portion of storage screen 12, irrespective of the character being presented.

Normally, the different distance of horizontal deiiection plates 49 from the lens 2li' will cause the successive paths 132 of the electron beam to cross over at points that form a locus which is spaced' from common point i341 ln the vertical plane shown, the locus of these points is indicated' by a dashed line 3.36 in Fig. 4. When this is the case, the center of deflection of the horizontal deiiection plates 68 is made to fal on the line i3d. Horizontal and vertical deflection voltage generators 76, Sti generate voltages which are impressed on deflection plates 68 and 70 to direct the electron beam to the particular portion of storage screen l2 on which it is desired to write the character.

ln ord'er to write on the storage screen, it is necessary to maintain a potential gradient from the storage surface to the iiat screen H2. This is effected by means of flood electrons produced by flood gun le. Flood electrons are directed uniformly over the entire storage Isurface to liberate fewer secondary electrons than incident primary electrons. in this manner, the storage surface is charged in a negative direction until it has reached the potential of the 'ood gun cathode 9?. Thus, a potential gradient is produced from the storage surface provided by dielectric material 1'l4' to the iiat screen H2.

When writing upon the storage surface, the character writing electron beam bombards an area of storage surface having a shape similar to that of the aperture in matrix mask 29 that it traversed. ln accordance with the tentative theory of operation, the highenergy electrons of the electron beameach liberate numerous additional electrons from their molecular bondsinI the molecular matrix comprising the dielectric material H4 which provides the storage surface. These' electrons are attracted through this molecular matrix tox thetiat screen M2 to charge the bombarded portion of the storage surface in a positive direction. In order for the charge to remain on the storage surface, it is necessary that the initial charge effected by the writ-ing' beam be greater than the critical potential of the storage4 surface; The iioody electrons then liberate more secondary electrons than incident primary electrons from the positive charged portions of the storage surface to` charge theseportions to the potential of the flat screen- 112". The horizontal' and vertical deilection voltage generators 7e and 80J successively move the electron beam from one portionto the next on the storage surface as the vertical and horizontal selection voltage generators 55 and 54' directY the electron beam through the selected character apertures in the matrix mask 20 to write the characters in sequence across the storage screen l2.

A visual image of the positively charged areas on thc storage surface is then produced on the viewing screen I4 by the action of the lood electrons. The contrast control grid is maintained at a sufficiently negative potential to prevent any field penetration from the high voltage of the' viewing screen when the storage surface is at the potential` of the ood gun cathode 9i), thus causing' the flood electrons' toV be repelled. When there is a positive charge on the storageV surface, however, the potential of contrast control grid' llt)Y is sufficiently positive so that there is iield penetration from the viewing screen through the storagev screenk 12, thereby enabling the ood electrons to' penetrate through the interstices of the positive charged areas of the storage surface and be accelerated towards the viewing screen 14 to produce a visual image of the characters written on the storage screen.

Thevisual' image of these characters may be maintained so long as the collector grid' 112 is maintained at apotential of the order of twice the critical potential of the storage surface material". When it isA desired tol erase the characters constituting the positively charged areas on the storage screen 12, it is only necessary to momentarily lower the potential ofthe fiat screen 112 to a potential that is less than the critical potential of the storage surface material and then raise it gradually back to its original value. ln this event, the potential' of the storage surface is returned to the potential of the flood gun cathode 90 by flood electrons, thereby creating apotential gradient from the storage surface to the flat screen 112, thus making the storage screen 12 ready for wn'ting by the character writing electron beam.

What is claimed as new is:

l. An electronic storage tube for thel visual presentation of information characters, saidtube comprising a storage screen including a foraminous conductive element, a layer of dielectric material that exhibits secondary electron emission' when bombarded by electrons disposedv on said foraminous conductive element, said layer of dielectric material' having arr exposed surface, and a flat conductive screen disposed in contact with said exposed surface, the portions of said exposed surface within the openings of said screen constituting a storage surface; means for producing an electronV beam; a matrix mask having a plurality of apertures, each of said apertures conforming to an information character; means for successively directing said electron beam through the apertures conforming to characters to be presented to make the cross sectional area of said electron beam successively conform to the configuration of each of the characters; means for maintaining said flat conducting screen at a first potential level; means for maintaining saidy storage surface at a second potential level negative with respect to said first potential level to produce a positive potential gradient from said storage surface to said at conductive screen; means for successively directing said electron beam to bombard predetermined portions of said storage screen to liberate numerous electrons within the bombarded portions of said dielectric material for each electron incident thereon whereby said liberated electrons are attracted to said at conductive screen by said potential gradient to produce a series of charge replicas of the characters to be presented on said storage surface; and means responsive to said charge replicas for producing a visual presentation of the information characters.

2. The electronic storage tube as defined in claim l wherein said means for successively directing said electron beam to bombard predetermined portions of said storage screen includes apparatus for producing an electrostatic lens for focusing said matrix mask on said storage screen whereby successive paths of said electron beam, in traversing the apertures of said matrix mask, cross over at a predetermined distance from said matrix mask, and electron beam deflecting means having a center of deflection at said predetermined distance from said matrix mask for directing said electron beam to said predetermined portions of said storage screen.

3. An electronic storage tube for the visual presentation of information characters, said tube Vcomprising means for producing an electron beam; a matrix mask having a plurality of apertures, each of said apertures conforming to an information character; means for successively directing said electron beam through the apertures conforming to characters to be presented to make the cross sectional area of said electron beam successively conform to the configuration of each of the characters; a storage screen including a foraminous grid structure, a layer of dielectric material that exhibits secondary electron emission and induced conductivity when bombarded by electrons disposed on said foraminous grid structure, said layer of dielectric material having an exposed surface, and a conductive screen disposed in contact with said exposed surface, the portions of said exposed surface within the openings of said screen constituting a storage surface; means for maintaining said conductive screen at a iirst potential level; means for directing Hood electrons emanating from a gun at a second potential level, negative with respect to said iirst potential level, uniformly over the area of said storage surface to charge each elemental area thereof substantially to said second potential level whereby a potential gradient is produced from said storage surface to said conductive screen; means for successively directing said electron beam to bombard predetermined portions of said storage screen to produce numerous conduction electrons within the bombarded portions of said dielectric material for each electron incident thereon whereby said conduction electrons are attracted to said conductive screen by said potential gradient to produce a series of charge replicas of the characters to be presented on said storage surface; a viewing screen disposed contiguous to and in register with said storage screen on the side opposite from said storage surface; and means for directing additional iiood electrons through the foramina of said storage surface contained within each elemental area of said charge replicas in a collimated beam to said viewing screen to produce a Visual presentation of said information characters.

4. The electronic storage tube as defined in claim 3, wherein said means for successively directing said electron beam to bombard predetermined portions of said storage screen includes means for producing an electrostatic lens for focusing said matrix mask on said storage screen whereby successive paths of said electron beam cross over at a predetermined distance from said mask, and electron beam deflecting means having a center of deflection at said predetermined distance from said mask for directing said electron beam to said predetermined portion of said storage screen.

5. The electronic storage tube as defined in claim 3 wherein said first potential level is positive with respect to said second potential by an amount equal to twice the critical potential of said dielectric material whereby said flood electrons charge all areas of said storage surface initially charged to at least the critical potential of said dielectric material to said first potential level.

6. The electronic storage tube as defined in claim 3, including a voltage generator coupled to said conductive screen for lowering the potential thereof from said first potential level to a potential less than the critical potential of said dielectric material and then to gradually increase the potential of said conductive screen back to said first potential level to erase said charge replicas from said storage surface.

7. An electronic storage tube for the visual presentation of information characters, said tube comprising a matrix mask having a plurality of apertures, each of said apertures conforming to an information character; means for producing an electron beam; means for successively directing said electron beam through selected apertures conforming to the characters to be presented to make the transverse cross sectional area of said electron beam successively conform to the configuration of the selected characters, respectively; a storage screen; means including apparatus for producing an electron lens to focus said matrix mask on said storage screen for successively directing said electron beam to predetermined portions of Y said storage screen to produce a series of charge replicas of the characters to be presented thereon; and means responsive to said charge replicas to produce a visual presentation of the information characters.

References Cited in the le of this patent UNITED STATES PATENTS