US2713648A - Image storage devices - Google Patents

Description

July 19, 1955 B. c. GARDNER IMAGE STORAGE D EVICES Filed March 6, 1955 ww. R. 2 DB Wu F 6 6 r 6 l 9 v. a 5 O llnov 5% 6| l l3 :F T M nun Lnlalw 7 \q H m 4,

501-152 CHARGE I I E WRITE 4 READ //v vE/vToR BERNARD C. GARDNER 3v 5% a] g ATTORNEY dtates atent Patented 511i .i. 2,713,648 TMAGE STORAGE DEVICES Bernard C. Gardner, Les Aitos, Califi, assignor to Raytheon P/lanufacturing Company, Newton, Mass, a corporation of Delaware Application March 6, 1953, Serial No. 341L747 7 Ciaims. (Cl. 315-42) This invention relates to circuits for electron tubes of the kind wherein an image can be stored in the form of an electrical charge pattern on a screen having a dielectric deposit on a pierced conductive sheet, and more particularly to circuits by which the charge pattern on the screen of such a tube is formed by making the dielectric deposit conductive by means of a modulated high-energy beam, the impact of which upon the dielectn'c causes the discharge of varying amounts of a previously deposited charge.

in image storage tubes of the type disclosed in United States Patent No. 2,547,638, issued April 3, 1951, to the applicant, where the writing beam scans the dielectric side of the storage screen, that has previously been given a uniform negative charge with the result that electrons are driven off by secondary emission to create a charge pattern determined by the varying energy of the writing beam, the writing time is relatively slow. This places a limitation upon the rapidity with which new information can be stored. When a charge is placed upon the dielectric deposit on a perforated conductive screen, it can be discharged in discrete areas by scanning the dielectric with a high-energy beam of electrons, causing the area struck to become conductive and permitting the charge to pass through the dielectric to the supporting conductive screen. The degree of this conductivity can be controlled by varying the intensity of the beam. This principle may be used for rapid reading of an image stored on a dielectric deposit on a very thin sheet of conductive material that is transparent to electrons. However, such screens are very difiicult to make successfully. In accordance with this invention, the principle of induced conduction by electron bombardment of dielectric deposits can be used for the rapid writing of information on a screen of the type described in the cited patent. When such a screen has been charged to a substantially uniform potential by an electron beam of relatively low energy, the information thus deposited can then be read by scanning the screen from the conductive side with a relatively low-energy beam of electrons that is collected after passing through the openings in the screen. The number of electrons passing through in a given interval of time is determined by the charge remaining on the dielectric material surrounding the openings through which the reading beam passes.

Other and further advantages of this invention will be apparent as the description thereof progresses, reference being bad to the accompanying drawings, wherein:

Fig. 1 is a longitudinal sectional view of a tube suitable for use in the circuit of the invention;

Fig. 2 illustrates schematically a circuit for the tube of Fig. 1 embodying the invention; and

Fig. 3 is a diagram of an enlarged part of the trajectory of an electron in a charging, a writing, and a reading beam in the region of the storage screen in the tube of Fig. 1.

Referring to Fig. 1, the reference numeral designates the envelope of the tube which may be of glass or other material. This tube has mounted in its left-hand end a charging and reading gun 11, and in its right-hand end a Writing gun 12 comprising a cathode 13, a grid 14, and a first anode 15 brought out through the seal to prongs 16, 17, and 18, respectively. The charging and reading gun 11 is of similar construction and is provided with a deflection coil 28 and a focusing coil 21. The

writing gun end also is supplied with a set of deflecting coils 22 and a focusing coil 23, shown diagrammatically in Fig. 2. The gun 11 is also provided with a second anode, in the form of a conductive coating 24 on the inside of the tube wall 19, which is connected to a source of potential through a terminal 25 embedded in the glass of the envelope 10. The storage screen 26, parts of which are shown more in detail in Fig. 3, is mounted in a ring which is supported within the envelope by studs 27 and 28. Stud 27 is electrically connected to a terminal 39 mounted in a glass envelope 1%}, and has fastened to it an insulating bead 31. A second insulating head 32 is also fastened to the stud 23. A second ring 33 is supported by two mounting studs 34 and 35, set in the beads 31 and 32, respectively, to maintain it in a plane parallel to that of the storage screen 26. The third stud 35 makes electrical contact with a second terminal 36 mounted in the envelope 16. A metallic screen 37 is mounted in the opening of the second ring 33. The dielectric surface 26a, of the storage screen 26, faces away from the metallic screen 37 and toward a second screen 38 mounted in a ring 46. This ring 41 is supported by two studs :1 and 42. The stud 41 is set in a third glass bead 43 attached to the stud 27, and the stud 42 is connected to a terminal 44 set in the glass envelope 10. The writing gun 12 is also supplied with a second anode, in the form of a conductive coating 45 on the wall Ill of the tube, which is connected to a terminal 46 set in the envelope Til.

The charging and reading gun 11 is connected to a source of positive potential, shown as a 300-volt battery 47 in Fig. 2, over a normally-closed set of contacts 48 controlled by the operator of switch 59, and to a source of negative potential, shown as a 300-volt battery 51, over a normally-open set of contacts 52 controlled by the operator of the switch 50. The screen 37 and the second anode 24 of the charging and reading gun 11 are connected to a source of positive potential, shown in Fig. 2 as an l800-volt battery 53, over a normallyclosed set of contacts 54, and over a set of normally-open contacts 55 to a tap 56 on this source, shown as having a potential of IZOD-volts in Fig. 2. The storage screen 26 is connected to a source of positive potential, shown in Fig. 2 as a 375-volt battery 57, over a normally-closed set of contacts 58 controlled by the operator of switch 50, and over a normally-open set of contacts 60 to a source of negative potential, shown in Fig. 2 as a 235- volt battery 61. The cathode 13 of the writing gun 12 is connected to a source of negative potential, shown in Fig. 2 as a 10,000-volt battery 62. The grid 14 of the gun 12 is connected to the cathode 13 through the output of a source of writing signals 63. The second anode 45 for the writing gun 12 is connected to the screen 38 through a source of positive potential, indicated in Fig. 2 as a lO-volt battery 64 and a resistor 65. The resistor 65 is connected to an output terminal 66 where the output signal is taken off.

In operation, when the switch 50 is in the charge position, a stream of electrons 7% is emitted from the cathode in the charging and reading gun 11, and is decelerated as it passes through the screen 37 and goes on through the openings in the storage screen 26 to the dielectric side 26a where it encounters the relatively negative potential of the screen 38 and is reflected back toward the dielectric side 26a of the screen 26 to impinge on the dielectric coating 26a to deposit a charge. This electron path is best seen in Fig. 3. As the screen 26 is scanned by the deflection system 20 of the gun 11, the dielectric deposit 26a assumes a uniform charge.

When the switch 59 is moved to the writing position, indicated by the dotted lines in Fig. 2, a beam of electrons, represented by the dotted line 71 in Fig. 3, is emitted from the cathode 13 of the writing gun'12 and is caused by the associated deflection system 22 to impinge on successive areas of the dielectric coating 26a on the screen 26. This cam is modulated by the source of writing signals 63 and strikes any given area of the target 26 with an energy depending upon the Writing signal at that time and the potential of the source 62. The effect of the impact of this high-energy beam of electrons on the dielectric deposit 26a is to make the dielectric conductive in the immediate region of the impact to an extent determined by the energy of the beam at that time. The effect of this conductivity is to cause any charge present in that area to flow through the dielectric to the conductive screen 26b, as indicated by the arrow 72 in Fig. 3. The stored information is then represented by the distribution of the residual charge on the dielectric layer 26a.

When the reading gun 11 is caused to scan the screen 26 in this position of the switch 5%, a beam of electrons is emitted from the cathode of the gun l1 and passes through the screen 33 and the openings in the screen 26. The charge remaining on the dielectric deposit 26a, in the immediate region to which the reading beam passes. determines the current density and velocity of this beam as it emerges from the screen 26 and is collected by the screen 38. The beam Current caused by the electron beam striking this screen 38 flows through the resistor 65 and the source of potential 51 to the cathode of the gun 11.

The secondary emission effect of the electrons striking the storage screen also plays a part in this tube. but the induced conduction in the dielectric material is the major effect involved in the writing operation. The result is a storage tube circuit having a very rapid writing rate once the uniform charge has been deposited upon the dielectric by the charging beam.

This invention is not limited to the particular details of construction, materials and processes described. as many equivalents will suggest themselves to those skilled in the art. It is, accordingly, desired that the appended claims be given a broad interpretation commensurate with the scope of the invention within the art.

What is claimed is:

1. In an electronic charge storage device, a perforated storage target having an electrically conductive side and a dielectric side, said dielectric material being of a type that becomes conductive when bombarded by electrons, means providing a first electron beam for scanning said dielectric side to produce a charge thereon. means providing a second electron beam of high velocity for scanning said dielectric side to render said dielectric conductive in the area of impingement thus reducing the charge on the successive areas of impingement to produce a charge pattern on said dielectric side. and means providing a third electron beam to scan said conductive side.

2. In an electronic charge storage device. a perforated storage target having an electrically conductive side and a dielectric side, said dielectric material being of a type that becomes conductive when bombarded by electrons, means providing a first electron beam for scanning said dielectric side to produce a charge thereon. means providing a second electron beam of high velocity for scanning said dielectric side to render said dielectric conductive in the area of impingement thus reducing the charge on the successive areas of impingement. means for modulating said second beam during scanning to produce a charge pattern on said dielectric side. and means providing a third electron beam to scan said conductive side.

3. In an electronic charge storage device. a perforated storage target having an electrically conductive side and a dielectric side, said dielectric material being of a type that becomes conductive when bombarded by electrons. means providing a first electron beam for scanning said target from the conductive side. and means to cause an electron of said beam which passes through said target to alter its course and impinge upon said dielectric side to produce a charge thereon, means providing a second electron beam of high velocity for scanning said dielectric side to render said dielectric conductive in the area of impingement thus reducing the charge on the successive area of impingement to produce a charge pattern on {I said dielectric side, and means providing a third electron beam to scan said conductive side.

4. in an electronic charge storage device, a perforated storage target having an electrically conductive side and a dielectric side. said dielectric material being of a type i that becomes conductive when bombarded by electrons, means Fro-viding a first electron beam for scanning said target from the conductive side, means to cause an electron of said beam which passes through said target to alter its course and impinge upon said dielectric side to produce charge thereon, means providing a second electron b am of high velocity for scanning said dielectric to render said dielectric conductive in the area of impingement thus reducing the charge on the successive areas of impingement, means for modulating said second beam during scanning to produce a charge pattern on said dielectric side, and means providing a third electron beam to scan said conductive side.

5. n an electronic charge storage device, a perforated storage target having an electrically conductive side and a dielectric side, said dielectric material being of a type that becomes conductive when bombarded by electrons, means providing a first electron beam for scanning said target from the conductive side, and means to cause an electron of said beam which passes through said target to alter its course and impinge upon said dielectric near the region passed through to produce a charge, means providing a second electron beam of high velocity for scanning said dielectric to render said dielectric conductive in the area of impingement thus reducing the charge on the successive areas of impingement, means for modulating said second beam during scanning to produce a charge pattern on said dielectric side, and means providing a third electron beam to scan said conductive side.

6. in an electronic charge storage device, a perforated storage target having an electrically conductive side and e a dielectric side, said dielectric material being of a type that becomes conductive when bombarded by electrons,

means providing a first electron beam for producing a uniform charge on said dielectric side, means providing a second electron beam of high velocity for scanning said dielectric side to render said dielectric conductive in the area or" impingement thus reducing the charge on the successive areas of impingement to produce a charge pattern on said dielectric side, and means providing a third electron beam to scan said conductive side.

i. in an electronic charge storage device, a perforated storage target having an electrically-conductive side and dielectric side, said dielectric material being of a type that becomes conductive when bombarded by electrons, means providing a first electron beam for producing a uniform charge on said dielectric side, means providing a second electron beam of high velocity for scanning said dielectric side to render said dielectric conductive in the region of impingement thus reducing the charge on n; the successive areas of impingement, means for modulating said second beam during scanning to produce a charge pattern on said dielectric side, and means providing a third electron beam to scan said conductive side.

References Cited in the file of this patent lUNlTED STATES PATENTS

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