US 3500102 A
Description (OCR text may contain errors)
March 10, 1970 M, E, CRQST ETAL 3,500,102
THIN ELECTRON TUBE WITH ELECTRON EMITTERS AT INTERsEcTIoNs oF cRossED coNDUcToRs Filed May 15, 1967 /NvENTo/as,
2 Mu/vsEY E. cRoST gg KENNETH sHouLosRs U BY #afa/S? ff f. VOLTAGE f Sabo-vu( ggf@ C. @H
ATTORNEYS United States Patent O 3,500,102 THIN ELECTRON TUBE WITH ELECTRON EMITTERS AT INTERSECTIONS F CROSSED CONDUCTGRS Munsey E. Crost, Allenhurst, NJ., Kenneth Shoulders, Woodside, Calif., and Mortimer H. Zinn, West Long Branch, NJ., assignors, by direct and mesne assignments, to the United States of America as represented by the Secretary of the Army y Filed May 15, 1967, Ser. No. 639,928 Int. Cl. H011' 1 62, 63/04 U.S. Cl. 313-109 2 Claims ABSTRACT 0F THE DISCLOSURE The thin electron tube is made possible by providing a cathode of an extensive surface area having a large number of densely packed electron emitters spread over the area. A grid of conductors is provided on the cathode for selectively exciting predetermined ones of said emitters. Pulses applied to the conductors of the grid will cause emission at the emitters located at the points of crossing where a coincidence of pulses occur. The cathode is scanned by the pulses thereby eliminating the need for a deecting beam to produce scanning of a target. An anode is provided at the target to impart a velocity to the emitted electrons in the direction of the target.
Background of the invention The present invention relates to electron beam devices and more particularly to electron display tubes, storage tubes, and video pick-up tubes.
In the field of television and radar, it has been the general practice to employ cathode ray tubes having one or more electron guns which product electron beams for exciting a phosphor screen in some predetermined pattern to display information thereon. The screen is scanned by detlecting the electron beams as the information is displayed by modulating the electron density of the beam. In the television eld, the modulating information is obtained originally from a camera tube such as a vidicon tube in which a charge density pattern is formed by photoconduction and stored on that surface of the photoconductor which is scanned by the deflecting electron beam.
Such prior art cathode ray tubes, camera tubes, and the like usually take the form of a rather long, funnelshaped vacuum tubes, to provide suicient room for deecting the beams of electrons. Those concerned with the development of such tubes have long recognized the need for a tube which would be relatively'thin. The advantages of a thin display or camera tube are rather obvious from a -geometrical point of view. However, thin electron tubes are advantageous from an electrical point of view also. For example, standard color displays use three electron beams which pass through an aperature mask before striking a phosphor dot screen. Proper deection of the beam is important to insure that the beam passes through the aperatures properly and is not aborted by the mask. It has been found, however, that standard color display devices are useless when moving in the earths magnetic field which causes unwanted deflections of the beam and degration of the color display. Of course, if the flight time of the beam was decreased to a negligible amount there would be little or no unwanted deflections.
One of the rnost critical problems confronting designers of thin electron tubes has been the elimination of the need for deflecting the electron beams for scanning purposes and reducing the flight time of the electrons. The present invention overcomes this problem.
3,500,102 Patented Mar. 10, 1970 rice Summary of the invention Brief description of the drawings The exact nature of this invention as well as other objects and advantages thereof Will be readily apparent from consideration of the following detailed description of preferred embodiments of the invention as illustrated in the accompanying sheet of drawings in which:
FIGURES 1 and 2 show a sectional view of two different types of electron emitters used in the present invention;
FIGURE 3 shows an isometric sectional view of a portion of the cathode used in the present invention;
FIGURE 4 shows a top view of a preferred embodiment of the present invention;
FIGURE 5 shows a sectional view taken on the line 5-5 of FIGURE 4, and
FIGURE 6 shows a graph of I vs. V.
Description of the preferred embodiments Referring now to the drawing, wherein like reference characters designate like or corresponding parts throughout the several views, there is shown in FIGURES l-5 a cathode 10 having a dielectric substrate 11 for receiving a plurality of spaced, thin-film conductors 12 which may be deposited or painted thereon in a well-known manner. A thin layer 13 of dielectric material covers the conductors 12. A second plurality of thin-film conductors 14 are spaced on the surface of film 13. A large number of electron emitters 15 are provided on the cathode 10. The structure ogn electron emitter 1S may be of several different forms two of which are shown in FIGURES 1 and 2. An emitter 15 generally consists of an opening 16 which extends through the upper conductors 14 and the dielectric 13 to the surface of the lower conductor 12. Provided in the opening 16 is a means which will emit electrons therefrom as a result of a suflicient voltage difference between the conductors 14 and 12- FIGURE 1 shows an emitting means which is made up of a plurality of conductive asperities 17 which extend into the opening 16 and terminate in a relatively sharp pointed tip. Field emission of electrons from the tips of these asperities, which may be microscopic or less in size, is possible because of the extremely high field strength or eld gradient which exists at the tips thereof when a voltage is applied to conductor 14. Of course, the voltage difference between conductors 12 and 14 may be relatively low while the field strength at the tips of asperities 17 may be extremely hig'h as a result of the microscopic dimensions of the asperities 17, the relatively small spacing between conductors 12 and 14, and because the tips of asperities 17 extend close to the aperture of openings 16.
The emitter shown in FIGURE 2 consists of a semiconductor 19 such as barium oxide placed in opening 16. The semiconductor 19 is placed in contact with the conductors 12 and 14. Transverse field emission will liow from semiconductor 19 when current of a proper value is passed therethrough. Electron emission of this type was reported in EDN, April 1967, pp. 14 and 15.
A representative portion of the cathode 10 is shown in FIGURE 3. The electron emitters 15 are densely spread over the surface of the cathode 10. Emission from a particular group of electron emitters may be accomplished by pulsing simultaneously one of the conductors 12 and one of the conductors 14 with voltages of a proper value. The coincidence of these two voltages at the point of crossing of the conductors 12 and 14 which have been pulsed, will produce emission, as explained above, from those emitters 15 which are located at the point of crossing. By sequentially pulsing the conductors 12 and 14 in some predetermined manner, the cathode 10 may be scanned in any of the well-known fashions. The grid of conductors 12 and 14 may also be arranged to obtain a radial scanning effects common to ppi radar scopes. For example, conductors 14 may be arranged as concentric circles and conductors 12 may be arranged radially.
The electron ltube may take the form shown in FIG- URES 4 and 5 -which shows an electron display device having a glass envelope placed over the cathode 10. On the inside surface of envelope 20 and opposite conductors 14 may be placed a target of a phosphor screen 21 having a thin aluminied coating 22. A conductor 23 extends through envelope 20 and into contact with coating 22. Coating 22 may act as an anode by placing an accelerating voltage on conductor 23. The envelope 20 is hermetically sealed (with an insulating seal material) to the top surface of cathode 10 after which the space in the envelope 20 is then evacuated.
When electrons are emitted from the emitters 15, as a result of applying signals to the ends of conductors 12 and 14 which extend out of the vacuum through the seal between envelope 20 and the cathode 10 thereof, the anode 23 will accelerate these electrons toward the screen 21. The number of electrons emitted or the electron density at a particular emitter will depend on the particular voltage difference between the particular conductors 12 and 14 as determined by the lI-V characteristic. A typical I-V characteristic for a eld emitter is shown in FIGURE 6. Therefore, information in the form of a video display may be produced on the screen 21.
It is pointed out that the screen 21 may also lbe made up of an array of phosphor dots or a series of phosphor lines which will emit at three different colors when excited and the conductors 12 and 14 scanned accordinglyto provide a color picture. With certain obvious modifications, the tube may be adapted to be a camera tube or a storage tube. For example, in the case of a camera tube, accelerating and decelerating devices may be incorporated to perform their usual function. With two cathodes placed on opposite `sides of a single storage target a storage tube may be provided which will permit scan conversion or other storage tube functions to be carried out. In all cases, however, the result is a tube which does not require a deflection device and the necessary space required for deflection; there will be a short flight path and an extremely thin geometry.
Obviously many other modications and variations of the present invention are possible in the light of the above teachings. It is, therefore, to be understood, that within the scope of the appended claims, the invention may be practiced otherwise than as specifically described.
What is claimed is:
1. The device according to claim 2 and wherein said semiconductor means is barium oxide.
2. An electron tube comprising a relatively flat extended dielectric substrate; a first group of spaced thin lm conductors mounted on one surface of said substrate; a thin layer of dielectric material mounted on said one surface and covering said first group of conductors; a second group of spaced thin film conductors mounted on the surface of said thin layer of dielectric material and substantially transverse to said first group of spaced thin film conductors; said second group of conductors and said thin layer of dielectric material having a plurality of concentric openings extending therethrough to form a plurality of cavities; the base of each said cavity including a portion of one of said first group of conductors; electron emitter means comprising a semiconductor means mounted in each said opening and in contact with said conductors of said rst group and said second group for emitting electrons upon the application of' a predetermined potential difference between the conductors of said first and said second groups; a transparent envelope mounted on said thin layer of dielectric material and spaced from said openings to form an evacuated chamber; the surface of said envelope inside said chamber and opposite said emitters `being covered with a thin conductive film and a uorescent screen; anda conductive electrode connected to said thin conductive film and extending through said envelope whereby electrons are accelerated from said emitters toward said screen upon the application of a voltage to said electrode.
References Cited UNITED STATES PATENTS 2,595,617 5/1952 Toulon.
2,117,842 5/1938 George 313-336 2,858,480 10/ 1958 Shadowitz.
3,091,719 5/1963 Dyke et al. 313-336 X 3,334,269 8/1967 Heureux 3l3-l08 X OTHER REFERENCES EDN (Electrical Design News); April 1, 1967; pp. 14-15.
ROBERT SEGAL, Primary Examiner U.S. C1. X.R. 313-299, 309