US3531681A

US3531681A - Flat display tube and method

Info

Publication number: US3531681A
Application number: US739819A
Authority: US
Inventors: Joseph T Harden Jr
Original assignee: JOSEPH T HARDEN JR
Current assignee: JOSEPH T HARDEN JR
Priority date: 1968-06-25
Filing date: 1968-06-25
Publication date: 1970-09-29
Anticipated expiration: 1987-09-29

Description

' Sept. 29, 1970 J. T. HARDEN, JR

FLAT DISPLAY TUBE AND METHOD 5 Sheets-Sheet J Filed June 25, 196e 1 Tm u M000000000000000000000v w ATTORNEY 3-1` 29, 19?@ J. T. HARDEN, JR

FLAT DISPLAY TUBE AND METHOD 5 Sheets-Sheet 2 Filed June 25, 1968 29, 1970 J. T. HARDEN, JR

FLAT DISPLAY TUBE AND METHOD Filed June 25, 1968 5 Sheets-Sheet 3 J. T. HARDEN, JR

FLAT DISPLAY TUBE AND METHOD Filed June 25, 1968 m UNGGGGGGG Dn DnDuDnDuRBDn 5 Sheets-Sheet 6 AV `AV R J N, E D R A H T.. Im

vToEU V Y A -53 AVAVAVAVVV? RING COUNTER CIRCUIT FLAT DISPLAY TUBE AND METHOD #Aw Www A Filed June. 25, 1968 Sandston, Va. 23150 Filed June 25, 1968, Ser. No. 739,819 Int. Cl. H01j 29/50, 29/72 US. Cl. 315-13 20 Claims ABSTRACT F THE DISCLOSURE A thin flat display tube in which a plurality of individual electron beams corresponding in number to the number of horizontal lines desired in a display are sequentially projected into a at narrow space and deflected onto a display screen. Such individual beams are produced by an elongated or linear cathode capable of controlled emission of electrons from selected points to form beams, each of which is controlled by electrostatically and sequentially controlling the acceleration and focusing of the pencil beam segments. Each beam is intensity modulated in accordance with image information contained in a received television signal, for example, or by other data to be displayed and/ or controlled. Consult the specification for other features and details.

This invention is related to flat television display tubes, and, more particularly, to flat or shallow depth image reproduction tubes and beam generation and scanning systems therefore.

In most known short depth or flat cathode ray display tubes (c g., envelope, electron source, accelerating and deecting structures and display screen) an electron beam is aimed along an edge of the display screen past a first series of deflection plates. Deflection of a beam into the space between the display screen and a second set of deflection plates is effected by potentials on one of the first deflection plates and impingement of the deflected beam under the display screen is effected by a potential on the second set of deflection plates. The point of impingement can be varied continuously by sequential variation of potentials on the respective deflection plates to produce, for example, a conventional television raster. Tubes generally of this type are disclosed in Aiken Pat. 2,795,731 and several beams may be controlled in a corresponding manner for control of color displays.

Multi-beam tubes are also disclosed in the patent literature as in Roberts Pat. 2,858,464. In Roberts patent the beam forming structure comprises an elongated cathode in a perforated or slotted tubular member which produces a plurality of beams or a sheet of electrons. A second tubular structure having a series of perforations angularly disposed with respect to the perforations or slot in the first tubular member surrounds the first tubular member and a deflection field is utilized to deect all electrons (beams or sheet) to cause sequential aligning of beams or segments of the sheet of electrons with the second series of perforations.

Objects of the present invention include providing improvements in thin, flat display tubes, an improved multibeam scanning device and method, primarily for use in flat display tubes and devices.

In accordance with the present invention, instead of it projecting one or several beams along the edge of the display area and then manipulating the beam for horizontal and vertical traverse of the display screen, a plurality of individual beams are generated, one for each line of a conventional television display raster by means of a linear cathode ray gun structure having means for individually focusing each individual beams and in which intensity control is effected by increasing or decreasing the bias on the emission electrode. Thus, the invention incorporates 3,53l8l Patented Sept. 29, 1970 a unique scanning device having a plurality of individualized electron beams each individually capable of being electrostatically controlled, focused, and accelerated into an area of the tube for deflection onto a fluorescent screen. The screen may be for direct View in the sense that the light produced is visible from the surface of the phosphor struck by the screen thereby reducing the energy requirements for a high light output. In addition, the scanning structure per se may be oriented so as to project one or a plurality of individualized beams along a path such that as the spot of light is caused to traverse a line of impingement on the display screen, the angle of impingement is substantially constant to maintain the shape of the light spot produced substantially constant.

These and other features, objects and advantages of the invention will become apparent from the following description taken with the accompanying drawings in which:

FIG. l is a prospective view of a shallow depth fiat display tube partly cut-away and illustrating the invention;

FIG. 2, 3, 4, 5, and 6 are exploded perspective views of a multi-electron beam forming, focusing and accelerating structure incorporating the invention;

FIGS. 7 and 8 are diagrammatical cross sectional views of a fiat display tube incorporating the invention;

FIGS. 9 and 10 are illustrations of a further embodiment of the invention;

FIG. 1l, taken with the wave form diagrams of FIGS. l2, 13 and 14 illustrate another aspect of the invention;

FIGS. l5-2() inclusive, illustrate a direct view application of the invention;

FIG. 2l is a diagrammatic showing of input circuitry and devices for use with a at display device incorporating the invention;

FIG. 22 is a circuit diagram of a shift counter circuit and output connections thereto for controlling the grid structure of the scanning device of this invention, and

FIGS. 23, 24, 25A, 25B, and 25C inclusive, illustrate one application of the invention to a color display.

The embodiment of the invention as illustrated in FIG. 1 comprises an envelope 20 which may be of glass, which may be made from two shallow shaped sections in the forms of shallow rectangular trays fused together along the contacting edges (not shown). Face plate 21 constitutes the viewing area of the tube and has the inner wall thereof a conventional phosphor coating 22 which serves as the viewing screen. The screen may be a simple phosphor or a combination of phosphors responsive to electron bombardment by scanning electron beam or beams to produce light and, unless otherwise noted, it will be assumed that such phosphors and screen structures are conventional.

Cathode 2S is an elongated indirectly heated emission cylinder (heating element not shown) having a conventional electron emissive coating thereon such as an oxide type material, and capable of emitting electrons along its length. Alternatively, the heating element itself may be coated with an oxide coating (barium or strontium oxide, for example) to constitute the cathode. Spaced from cathode 25 are a series of emission control grids 26 coacting with a slotted emission control plate 27, slot 28 in plate 27 having a length substantially along the length of cathode 25. Grids 26 and slotted control plate 27 are effective when proper potentials are applied thereto, as described later, to effectively cut off emission from the cathode except for a selected area or point Where emission is desired. Further, this grid control structure is capable of controlling emission from any point along the length of the cathode or from several points from the entire length of the cathode simultaneously, if this be desired. Thus, there is no significant loss of energy as the beam dividing srtucture is capable of controlled emission along its length. While this 3 control function and structure effectively turns olf the rest of the cathode emission while emission is occurring at only one point. It will be apparent that groups of grid elements may be assigned independent display control functions and, accordingly, may lbe controlled independently, as groups, with a separate control plate therefor.

Emitted electrons drawn from the region surrounding the cathode to the emission grid plate control structure by virtue of positive potential placed upon the emission grid, travel toward the emission grid and gain velocity and momentum. When electrons reach the emission grid, a great number of electrons strike the grid and are retained but some travel through the vertical slit or slot 28. Spaced from slot 28 is a focusing and accelerating assembly 29 which contains an individual focusing and accelerating structure for each individual beam passing through slot 28. The focusing and accelerating structure electrostatically focuses each beam into a thin pencil beam, the focal point of beam being the fluorescent screen. Since the distance between the acceleration anode and the screen varies generally linearly) the focusing field will be varied in order to keep the focal point moving continuously on the screen. It is possible to focus the beam magnetically instead of electrically, however, electrostatic focusing is preferred.

After focusing, the individual beams pass through the accelerating anode where high positive potentials give the electrons energy and velocity necessary to produce visible light on the display screen.

As shown in FIG. 1, each beam thus formed, focused and accelerated is deflected by a pair of

deflection plates

30 and 31 which have proper deflection potentials applied thereto to cause the beam to traverse a horizontal line of impingement 32 which is substantially parallel to one side wall of the fluorescent screen 22. In general, in order to maintain uniform impact or impingement velocity as the beam is caused to traverse along the line of impingement, the beam must vary in angular velocity at its departure from the

deflection plates

30 and 31. Hence, instead of a conventional saw-tooth deflection waveform, a parabolic shaped waveform is preferred such as shall be described more fully hereafter.

The multi-electron beam forming focusing and accel erating structure shown in FIG. l is shown in detail in FIG. 2 wherein a ilat header or closure plate 35 has extending therefrom support posts 36, 37, 38, 39, respectively. Header plate 35 may form the end closure for a flat envelope and all leads may project through header plate 35 by means of conventional glass-metal seals, not shown. It is apparent that it is not necessary or critical that leads from electrical supplies and/or control potentials exit from the tube through header plate 35 but they may exit from other portions of the tube. Cathode 25, grid structure 26, slotted plate 27, focusing and accelerating structure 29 and

deflection plates

30 and 31 are spaced along insulating support rods 3639 more closely than is shown in FIG. 2, this spacing shown in FIG. 2 being for purposes of illustration only. Elongated cathode is supported by a pair of support struts or

straps

41 and 42 so that it is substantially parallel to header plate and, as described earlier herein, cathode 25 may Ibe of the indirectly heated or directly heated type, the leads for heating elements not being shown in FIG. 2, it being understood that such leads being carried to the outside of the envelope through conventional glass-metal seals in header plate 35.

Control grid structure 26 comprises rectangular grid frame F, having grid wire posts P supporting a plurality of grid wires 26-1, 26-2, 26-3 26-410 each of which has a separate grid control lead 43-1, 43-2, 43-3 43-10, each grid lead exiting from the header plate 35 through a glass-metal seal, to provide pins 44-1, |44-2, 44-3, 44-10 for connection to a control circuit to be described later herein. Spaced from grids 26-1, 26-2 26-10 is a slotted emission control plate 27 having slot 28 therein which cooperates with the grid wires to define individual electron beams. A number of electrons drawn from the region of the cathode by virtue of positive potentials supplied on a selected emission grid element 26, pass through slot 28. It will be appreciated that there will be one beam for each line of the raster on screen 22. Each beam thus formed is focused and accelerated by focusing and accelerating structure 29. Slotted plate 27 is mounted on insulating support posts 36, 37, 38 and 39 by passing through mounting holes in the plate. As described earlier, conductors for supplying potential to emission plate 27 is by means of a conductor, not shown, passing through the header plate 35.

Focusing and accelerating anodes 29B and 29A may be constituted by a pair of conductive plates 29A and 29B. Plate 29A has an aligned vertical row of beam passages apertures 46-1, 46-2, 46-3, 46-N corresponding in number, and aligned with the beam passing spaces between grid elements 26-1, 26-2, 26-3 26-N. Likewise, plate 29B has a series of aligned apertures or passages 47-1, 47-2, 47-3 47-N, the passages 47 being aligned with the passages 46 and defining therebetween focusing lens structures for each individualized electron beam passing through slot 28, respectively. The preferred forms of these elements are shown in greater detail hereinafter but it suilices for present purposes to state that these structures electrostatically focus and accelerate each beam into a thin pencil beam and that the relative potentials between the plates 29A and 29B may be varied in order to dynamically maintain the point of focus of each individual beam, as it tranverses the line of impingement 32, at the point of impingement. Thus, as the beam impinges upon the screen 22 it will be continuously in focus. Dynamic focus in display tubes is well known in the art with respect to large area displays. However, since the variations are substantially linear in tubes made according to this invention, the matter of dynamic focusing is simplified. It will also be understood that after focusing, the beam passes through the accelerating anode 29A and the applied high positive potential on anode 29A give the electrons the energy and velocity necessary to produce visible light on display screen 22. Finally, in a simplified form shown in FIGS. 1 and 2, the beam is caused to traverse the line of impingement 32 on display screen 22 by means of a pair of

dellection plates

30 and 31 which have proper dellecting potentials applied thereto. For example, the plate 30 may have a positive potential applied thereto so as to deflect the beam from travelling directly parallel to the screen to where it impinges the display screen by means of a stronger positive potential applied to plate 30` than is applied to plate 31. The orientation of

dellection plates

30 and 31 and the electron source structure shown in FIG. 1 project beams which would normally impinge at varying acute angles as the bearn traverses fluorescent screen 22, so that due to this varying angle of impingement, the size of the light spot produced may vary according to the position of the White spot along the line of impingement. However, this effect is obviated by structure and manner of operation to be described later herein, it being the purpose ofthe present discussion to explain basic aspects of the invention.

With reference now to FIGS. 3, 4, 5, and 6, preferred forms of the focusing and accelerating electrode structure 29 will be described. With reference to FIG. 3, the focusing and accelerating anodes comprise a rst conductive metal plate 50 in which a series of holes or apertures 51-1,

51-2, 51-3 51-N have been drilled or otherwise formed and into each of holes 51-1, 51-2, etc. is press fitted cylindrical metal tubes 52-1, 52-2, 52-3 52-N,

respectively. Similarly, conductive metal plate 53 has a similar series of holes 54 into which similar cylinders 55 have been tted.

Anode plates

50 and 53 are separated by an insulating plate 56 made of mica, ceramic or other insulating material which has elongated slot 57 of a length to accommodate all of the holes 51-1, etc. and 54-1, etc. and these anode plates may be adhered to or otherwise fixed in relation to each of the side block 56. The structure may then be supported by support posts such as support posts 36, 37., 38, and 39 as shown in FIG. 2.

In practice, there is a large potential difference between the focusing anode 53 and accelerating anode 50- (several thousand volts). This causes a fringing or convergentelectrical field to be set up between the interior surfaces of the two coaxially aligned cylindrical anodes. The convergent electrical field lines between the pairs of anode cylinders has a convergent lens effect on an electron beam passing through the cylinder pair and by holding the voltage on the accelerating anode 53 constant (to maintain the velocity of the electrons constant) and raising or lowering the voltage on the focusing anode 50, the field can be made more or less convergent. By varying the potential difference between the focusing anode 50 and the accelerating anode 53, the focus can be continually changed through the horizontal sweep as the required focal length shortens as the impact or impingement point of the electron beam nears the multi-electron beam source. It should be noted that the potential at both anodes are substantially constant with respect to the cathode. Further, it should be noted that the focusing characteristics of every anode cylinder pair are identical at any time but that only the anode pair in which an electron beam is passing has any effect on the beam focusing. As noted earlier, when the beams are grouped, and assigned independent display functions, the anode plates therefor may be made .electrically separate for independent control.

Instead of using cylinders as described in connection with FIG. 3, the anode members (focusing and accelerating) may be made in accordance with structure shown in FIG. 4. In this case, focusing anode 50 may be a solid block of metal 55 and the cylinders 52 being constituted by the walls of the holes 51-1, 51-2' etc. Similarly, accelerating anode 53 may be constituted by a similar block of metal having similar holes 54-1, 54-2 etc. therein. Alternatively, the focusing and acceleration electrode structure may be formed in accordance with the arrangement shown in FIG. 5 whereby the anode plates 50 are drilled with apertures 51-1, 51-2 51-N", formed therein and cylinders 52-1, 52- and 52- are carried therein, but not flush with one side or the other of the plates. Accelerating anode 53 has apertures and cylinder inserts similarly formed, and insulator plate 56 is thickened somewhat to accommodate the projection of the cylindrical inserts. Moreover, it is apparent that the anode cylinders may telescope, one within the other. In this case, there is compensation for the capacity of the set that the inner faces of the

anode plates

50 and 53" have for one another. FIG. 6 is a variant showing the elimination of the insulative substrate 56, spacer posts 36, 37", 38 and 39 being portions of

support rods

36, 37, 38 and 39 of FIG. 2, for example. It will be appreciated that the focusing and accelerating anode structure may be made simply by boring aligned series of properly shaped holes in an insulating substrate and depositing or otherwise applying conductive metal surfaces thereon to form the focusing lens and accelerating anode structure or a nonconductive substrate may be formed with opposed rows of cavities, filled with conductor material and the bored to provide electron beam passage. Thus, variation in lens design is possible within the framework of the present invention it being important that the structure has the focusing and acceleration characteristics desired herein.

It was mentioned earlier that when the electron beams are caused to traverse a line of impingement on the display screen, the angle of impingement, in accordance with the embodiment disclosed in FIG. l, varies as the beam is caused to traverse the line of impingement thereby varying slightly the horizontal shape of the light spot as it traverses the line of impingement. In order to eliminate and minimize this effect, the beams may be bent or deflected by a single deflection element or a plurality of deflection elements oriented in opposed relation to the display screen. Thus, with reference to FIGS. 7, 8 and 9,

cathode 25, grids 26, and focusing and acceleration anodes 29, eg., the multi-beam forming structure, is deposed at an angle a (FIG. 7) to aline parallel to the display screen 22. In this instance, a planar deflection plate or electrode 60, which may be a conductive coating on the rear Wall v61 of envelope 20, cooperates with a deflection grid 62 to bend or deflect the beam toward the display screen 22. (Although deflection grid 62 is shown in the space between deflection electrode 60 and the display screen, it will be appreciated that grid 60` may be a transparent conductive coating on face plate 22.) Only one electron beam is shown in FIG. 7 but all beams have similar trajectories. In operation, as the lbeam leaves the accelerating and focusing anode structure 29, the electron beam passes between deflecting plate 60 and deflecting grid 62 the deflecting plate and the deflecting grid have applied thereto a varying electric field to establish a varying electrostatic field generally perpendicular to the direction of electron beam travel, e.g., transverse to the direction of travel of the electron beam. If the deflection plate 60 is negative and the deflecting grid 62 is made positive the electrons will be deflected and accelerated toward the deflection grid l62. This will result in the electron beam being bent or deflected toward the deflection grid 62 and passing onto the grid structure and striking the viewing portion or screen 22 to emit light where the electrons strike. It is known that electrons projected through a region perpendicular to an electrostatic field follow a parabolic trajectory, so it can be seen from FIG. 8 that the angle x of impingement of the electron beam on display screen 22 can be held more uniformly constant by making the configuration of the deflection plate conformal to a plate extending over the entire wall 61 of the tube and a grid 62 extending at least across the rear of the viewing screen. As shown in FIG. 7, the angle of incidence or impingement is made even more uniform if the electron beam is projected at a small angle a towards the rear of the tube, e.g., at an angle of plus a to the display screen 22. As described earlier herein, focusing will be continually compensated throughout the sweep cycle by adjusting the focusing potential between the focusing anode and the accelerating anode.

Further, it is believed that a uniform angle of impingement may be effected by utilizing the continuous deflection plate 60 illustrated in FIGS. 7 and 8 by curving or canting the deilecting plate toward the screen which will cause the electron path to bend only |gradually while passing through the region of the deflecting plates near the electron source but to bend severely towards the far end of the deflection plate, thus, tending to equalize the impinging angle.

FIG. 9 is somewhat similar to the structure shown in FIG. 8 except here instead of a continuous deflection plate 60, the deflection element has been broken up into a plurality of deflection elements '70-1, 70-2, 70-3 70-N (beam forming, focusing and accelerating

structure

25, 26 and 29 being shown separately in diagrammatic form). Deflection electrodes or elements 70 may be in the form of simple vertical or elemental stripes made of transparent conductive material which may be deposited on a nonconductive substrate or supporting surface, as for example, the rear wall of 61 of the tube.

As in the case of the embodiment shown in FIG. 8, the electron beams entering the region between the deflection electrode elements 70 and deflection grid 62 travel in a straight line to a point at which an electrostatic eld has been established between one of deflection elements 70-1, 70-2 70-N. By initially producing or establishing this electrostatic field near the far end of the tube remote from the electron beam source, and moving the field by increments toward the electron beam source, the beam may be made to traverse the display screen much in the same manner as is described in detail in the aforementioned Aiken patent. This approach, of course, required an additional sequential triggering or commutating circuit to be used to vary the defiection field across the face of the tube. However, this does have the advantage that the angle of irnpingement stays very uniform since the electron beam has very little deflection force applied to it until it approaches near the vicinity of the impact or impingement area of screen 22. FIG. 10 is a top view of the scanning device showing the path of the electron beam in this modification.

FIG. 1l is a cross section view showing another modification of the invention wherein two or more electron sources, at least one on each end of the tube are utilized to provide horizontal scanning. In this instance, a first multi-beam source A, identical to ones described earlier herein, projects its beams from left to right Whereas a second multi-beam source B projects its beams from right to left (or vice versa). Multi-beam source A may, for example, be arbitrarily designated as the beam source to supply odd-numbered horizontal traces whereas multibeam source B may be arbitrarily designated to supply even-numbered horizontal traces to thus provide interlaced scanning. In this way, any lengthening or change in light spot shape or dimension will be adjacent to a shortened light spot so that this has the tendency to blend or compensate the two images together and the picture will appear. An alternate practice would be to superimpose the two traces and reduce the intensity of the traces. In this way, bright spots, in order to appear very bright, would have to be made of two light traces superimposed upon each other. As can then be seen, only the narrow part of the beam will show clearly and the broad part of the beam will be rendered only faintly visible, if at all. A further compensation would be to intensify the electron beam from the source near the present position of the trace while weakening the electron beam from the other source.

It should be appreciated that in connection with FIG. 1l showing the second multi-beam source, that greater resolution may be effected by providing more horizontal lines. Thus, alternate scanning coupled with interlaced scanning can be accomplished. In alternate scanning, one source, source A for example, could supply lines 1, 5, 9, etc. and lines 2, 6, 10, etc., while the other source, source B, would supply lines 3, 7, 11, etc. and lines 4, 8, 12, etc. This expedient could simplify the construction of small size television tubes. Of course, each beam source is offset vertically (relatively) with respect to beams from an opposite source. It will likewise be apparent that use of plural multi-beam electron sources makes it easier for an electron beam to irnpinge upon a designated phosphor for any color television tube (as shown, for example in FIG. 23). For interlaced scanning, typical proximate waveforms are shown in FIGS. 12, 13 and 14. In FIG. 12, the approximate waveform used for sweeping the trace from the source B through interlaced scanning is illustrated, and FIG. 13 shows the approximate waveform used to sweep the beam emitted from source A while interlaced scanning is utilized, whereas the waveform illustrated in FIG. 14 would be used for alternate scanning. It is not necessary that the beam source or sources be located to the right or left side of the screen, illustrations heretofore described being merely illustrative. In fact, it is contemplated that the electron beam source run along the bottom of a display screen, e.g., the elongated cathode running horizontally along with the associated emission control structure and the focusing and acceleratin-g structure. In fact, this may be advantageous where the vertical dimensions of the display screen is less than the horizontal dimension. Thus, simply projecting the beams upwardly while moving the electron emission point from left to right, the vertical elongation of the trace, may be of less magnitude than the horizontal elongation of the trace due to varying angles of impingement simply because of the lesser distance involved. Of course, in this approach, the electron beam will be turned off and on, being displaced stepwise during off times so as to trace an image composed of a rectangular array of dots in a pattern much like a half tone newspaper photograph. Functionally, such beams would be projected upward to a certain elavation, the beam would traverse from left to right and then be cut off. Then, the beam would be projected upward to a point slightly lower than the previous trace and then traverse a horizontal line from left to right and repeat. Moreover, there may be multiple beam sources at the right and left side of the screen as well as along the bottom (and top if desired) so as to effect color display (FIG. 23), the beams from the respective sources seeking out their own color phosphors from different directions.

The embodiments described above are indirect displays in that the beams strike the phosphor of the display screen on a side or surface opposite the viewing side or surface. In accordance with the embodiment illustrated in FIGS. 15-20, the phosphor display screen is viewed from the side or surface struck by the electron beams. In FIG. 15 the multi-beam source designated generally with the numeral includes cathode, emission control structure and focusing and accelerating anode structure as described earlier herein. Likewise, as described earlier, the electron beams enter the region between the dflection plate 71 and deflection grid 72 and is deflected thereby in amounts and direction according to the direction of the electrostatic field between these deflection elements. The present arrangement differs from those described earlier herein in that the deflection plate 71 is in the form of a conductive layer deposited on a nonconductive substrate or support surface, such as the rear wall or panel of the tube. In this case, however, the fluorescent phosphor (not shown) is deposited directly upon this conductive layer. Further, the deflection plate 71 has a positive potential applied thereto Whereas the defiection grid 72 may have a negative potential applied thereto or even so that in effect electron beams are directed to impinge upon the fluorescent phosphor screen and the image may be viewed through the deflection grid 72. Due to the high incidence of peripheral light, the grid will not be particularly noticeable. In any event, the grid may be applied to the interior tube surface 73 in the form of transparent conductive material (and in some cases both deflection electrodes may be applied on exterior envelope surfaces). The advantage of this construction and manner of operation lies in its reduction of the amount of energy usually required to produce an equivalent amount of light output and more efficient utilization of light produced. Conventionally, an electron beam strikes on the screen with high velocity and has to force its way through a metallic layer into the phosphor coating in order to create light. The light energy discharged then has to travel through the phosphor to emit visible light that can be seen by the viewer. By bombarding the surface which is to be viewed instead of the non-viewing surface, significant savings in energy can be obtained and the energy available is more effectively utilized. In addition, lower electron velocities can 4be utilized and therefore lower focusing and deflecting potentials are required, all with attendant benefits in making the equipment portable or operable from low energy sources and the utilization of smaller components. FIG. 16 is a diagrammatic view of the arrangement shown in FIG. 15, the observer being designated O. It will also be appreciated that instead of a single deflection plate 71, multiple deflection elements illustrated in FIG. 9v may be utilized and this is diagrammatically illustrated in FIG. 17.

FIGS. 18 and 19 are modifications of the embodiment illustrated in FIG. 7 to illustrate applications of the direct view principle illustrated in FIGS. 15 and 16 with the multi-beam source 80l being contained within an offset section 20S of the tube 20. FIG. 20` is a further illustration of the modification of the invention shown in FIG. 7 as applied to the direct view principle described herein.

With respect to FIGS. 18 and 19, offset 20S has been introduced into the tube 20 in order to get the multi-beam electron source or gun 80 angled to place the point at which the electrons exit the accelerating anode flush with the viewin-g screen 2-2. The reason for this is the fact that an electron entering an electrostatic field follows a parabolic path. If the screen surface is flush with the electron gun, the electron ray will strike the screen at the same angle with which it enters the field no matter what portion of the screen it strikes. In other words the impinging angle of the electron beam remains constant as the point of impingement varies across the screen.

Calculations were made for a tube with a display area of 45 cm. x 30 cm. (17 in. x 11.8 in.). Results indicated that a tube measuring 6 cm. (2.35 in.) from front to rear face could accommodate a projection angle of 24.4 (say 20-25 A tube measuring 8 cm. (3.15) could accommodate a projection angle thus on equal impinging angle of 31.1 (say 25 31 While a little steeper angle is preferred, a 30 angle is satisfactory particularly if the electron beams instead of being formed of essentially circular cross sectional area were to be shaped of a rectangular or elliptical nature with the major axis running vertically.

lReferring to FIG. 20, between the viewing screen 22 and the deflection plate 71". There is .a deflection grid 72D substantially flush with the beam emission end of the multi-beam electron gun '80' and the gun is aimed to the rear of the tube. The electron bea-m will return to the region of the deflection grid 72D at the same angle at which it entered the field between the deflection grid and the deflection plate. For a distance of 4 cm. 1.58 in.) between the deflection grid 72D and deflection plate, the entry (and exit) angle is about 20. [Another electrostatic field shall be formed between the deflection grid 72D and the screen 22 and deflection electrode 71. Since the electron beam always enters this field at the same angle (about 20) if the field between the deflection grid and screen is kept `at a constant intensity the electron beam will always follow the same behavior in this field. This means that the electron beam will always strike the screen at the same angle.

To recapitulate, the electron beam enters the -field between the deflection grid and deflection plate at a constant angle, travels in a parabolic trajectory and exits the eld at the same angle with which it enters. Upon entering the second field between the screen and deflection grid, the electron beam still travels a parabolic trajectory, but a different parabola. If the field between the screen and deflection grid remains steady with respect to time, the electron beam shall always follow an identical path Ibetween the deflection grid and screen. Thus, if the angle of entry into the field never varies, the angle of exit (or impact angle on to the screen) never varies.

Using a distance of 2 cm. (.79 in.) from the deflection grid to the screen and on entry angle of 20 potential of 4,500 volts between screen and grid produces an impact angle of about 45 onto the screen. A potential of 30,000 volts between screen and grid produce lan angle of impingement of 75 which is nearly vertical. An angle between 45 and 75 should certainly be acceptable. Thus a tube thickness of 6 crn. (2.36 in.) and smaller is achieved. Of course, where this back `aiming is not used the tube thickness will be smaller.

Horizontal sweeping shall be accomplished by varying the voltage between the deflection plate and deflection grid. The voltage between the deflection grid and the screen shall remain constant.

lIt will be appreciated that the multi-beam source and method described herein may be utilized for many types of display systems, as for example, to reproduce fixed characters and/or other shaped images or scoreboard columns, computer readouts, metering devices, wherein a flat display is desired.

The tube structure and multi-beam scanning devices described earlier herein may be effectively utilized by adapting circuitry well known in the art. In order to illusstrate this, reference is made to FIGS. 2l and 22. Specifically, FIG. 21 is a block diagram of external circuitry associated with a display device of the present invention as applied with respect to conventional television signals. Thus, a receiving circuit includes a conventional antenna 90, for receiving conventional transmitted television signals and supplying same to receiver circuit 91. The receiver circuit 91 contains the conventional devices for home television receivers, for example, such as the usual RF and IF amplifying sections, detecting and control circuits and standard audio circuitry. Picture information is fed from receiver circuit 91 to video amplifier 92 and video amplifier 92 applies amplified video signal between emission control plate yand the cathode to control the intensity of a beam and, accordingly, the brightness of the trace in essentially the same manner as effected in conventional television receivers. With reference to FIG. l the video information is applied between emission plate 27 and cathode 2S. As noted earlier, the audio circuitry is conventional and since it has no part in the present invention, it is not disclosed herein.

Further, control information is fed from receiver circuit 91 to sync separator circuit 93 from which horizontal sweep pulses are applied to horizontal sweep generator 94 which produces the horizontal sweep voltages applied to the deflection plates.

Vertical sync pulses are also fed from the sync separator circuit 93 to the grid controlling circuit 95 described in greater detail in connection with FIG. 22. IIt should be noted at this point that if a ring counter type circuit is used as a grid controlling device, horizontal sync pulses can be used to trigger the grid controlling circuit and the vertical sync pulses may, for the most part, be ignored.

As noted earlier herein, the focus will be continually modified so as to compensate for the different distances from the acceleration anode to a point of impingement on the screen so periodically varying voltages will ybe applied across the accelerating and focusing anodes. Accordingly, an output from the sync separator circuit 93, the horizontal sync pulses are utilized to trigger a focus cornn pensation generator 96 which produces a varying voltage applied to the focusing anode. Alternatively, control of focus compensation circuit 96 may be obtained from the horizontal sweep generator, as is shown by connection 89..

With reference now to FIG. 22, vertical sync pulses from sync separator 93 are fed into a bistable multivibrator 97 which is control gate for controlling a pair of ring counters 98 and 99, respectively, which are used to effect sequential switching of the control grids, one ring counter circuit 98 being utilized to control odd numbered grid elements and the other ring counter 99 being used to control even numbered grid circuits, depending on the steady state condition of control flip-flop 97. As shown in FIG. 22, outputs of the ring counters are applied through coupling circuits, such as transistor followers T1, T3, T5 etc., to the grid elements. Thus, if pulses are fed into ring counter 98, the pulse signal will sequentially pass from coupling transistor T1, T2, T3, T4 etc., for the total number of stages desired and then on the activation of the final stage in the ring counter, the control flip-flop gate circuit 97 will be reset into its other steady state condition to thereby permit counter pulses to pass through the gate into ring counter 99 and control the interlacing of scan line. In operation, lall transistors except a selected one are off so a negative potential V) has been placed on these grid wires. With the selected transistor on, the grid connected thereto has a positive potential with respect to the cathode to permit electrons to flow in the region of the grid wire having the positive potential.

It will be appreciated that instead of using a control gate such as flip-flop 97, a single shift register with odd numbered control grids connected in sequence to the first l l stages of the shift register and the even sequence of control grid wires Connected to the last half of the shift register with the last stage of the shift register producing a feedback signal for resetting the shift register to re-initiate the sequence may be used.

Use of integrated circuitry reduces the size of this eX- ternal circuitry to very small dimensions. It is possible that other logic type circuitry may be used to control the grid voltages such as binary counters, delay lines, time delay circuits etc., and the like or a combinaton of these circuits the only essentiality being the sequential controlling of the `grid voltages.

FIG. 23 shows the rear surface of a television screen 122 with three linear multi-beam cathodes (control grid and focusing and accelerating electrodes being omitted for clarity) arranged along the sides and the bottom and designated Blue, Red, and Green. The screen 122 is composed of a plurality of four sided pyramid shaped structures 123 which have been formed by molding, etching, grinding or any other process indigenous to the glass markers art. The left side or facet of the pyramids (as seen in FIG. 23) are coated by a phosphor material that emits blue light when excited by an electron beam. The right side or facet is coated with a phosphor that emits red light and the bottom side or facet is coated with a phosphor that emits green light so that any color is produced by the combination of the three colors.

As can be seen, it is impossible for any electron beams emitted from say the red multi-beam source to strike anything other than a red light producing phosphor. Therefore shadow masking and other methods used to keep the red on red, green on green etc. are dispensed with. Mixing of colors by varying intensity of the electron beams can be done with conventional color TV circuitry.

Scanning can be done by either sending the chrominance information through a frequency trippler circuit and scanning alternately red, blue, green thereby rendering each image field composed of 3 subfields and each frame composed of 6 subfields. Or scanning may be accomplished by each color gun projecting its respective beam simultaneously and having the three beams converge toward a single area where a strong field is set up between the screen and deflection plate. This will require segmenting the deflection plate both horizontally and vertically, but control of the potential across each individual segment of the deflection plate can be made auxiliary to the circuits controlling the grids of each cathode.

FTG. 24 illustrates another method for producing a color picture is to utilize only one multi-beam electron gun and have alternate strips of red 130, green 131, and blue 132 light producing phosphors deposited on the screen in horizontal lines. Behind each red strip and behind each blue strip, there is a horizontal wire. The wires behind the red strips are connected together by but 135 and the wires behind the blue strips are connected together by bus 136. The end leads 138 and 139 of the secondary 137 of a center tap transformer are connected, end 138 to the red wires, and end 139 to the blue wires, respectively. A large potential difference is placed between the center tap 140 and the screen (not shown). The primary (not shown) of the transformer is excited with an AC voltage of 3.58 megacycles. As seen in FIGS. A, 25B and 25C, when the AC signal is going through zero the beam falls only on a green stripe. The color information for green only is placed across the multi-beam electron gun at this time. When the signal swings toward positive on the blue wires, only the blue stripe is illuminated and at this time only the blue color information is placed on the electron gun. When the signal swings toward positive on the red wire only the red color is displayed and only red color information is placed upon the electron gun.

The 3.58 megacycles signal causes the electron beam to oscillate vertically as it traverses the screen horizontally as can be seen by FIG. 25. The green portion of the color picture is excited twice as often as the red and blue colors, but for only half as long. This necessitates that the green color information 'be run through a frequency doubler and this signal used to gate the electron beam. This method of color reproduction is the method used on the ychromation or Lawrence type tube and is only briefiy described herein for purposes of illustrating the wide utility of the invention.

While there has been shown and described in detail the fundamental novel features of the invention, it will be understood that many variations are possible, some of which have been disclosed herein, and that Various other modifications and changes in the form and details of the invention may be made by those skilled in the art without departing from the scope and spirit of the invention.

I claim:

1. In a flat cathode ray display tube a flat envelope having front and rear walls and having an electron responsive display screen adjacent a wall thereof, a multibeam electron gun assembly for producing a plurality of individually controllable electron scanning beams projectable along parallel paths between the said front and rear walls, respectively, to impinge on said display screen along lines of impingement, respectively, comprising,

an elongated electron emissive cathode at one side of said envelope,

control electrode means for controlling the intensity of electrons emitted from said elongated cathode,

a grid structure for controlling emission of electrons from said cathode at any selected point along the length thereof, said grid structure being between said elongated cathode and said control electrode means,

focusing and acceleration electrode means for focusing and accelerating electrons emitted from any selected point on said elongated cathode, said focusing acceleration electrode means including a pair of conductive plate members supported in spaced relation to each other, each plate having a plurality of apertures therein aligned with said elongated cathode, the number of apertures in each of said plates corresponding to the number of lines of impingement upon said display screen, and

means for deflecting a selected beam issuing from any of said focusing and acceleration electrode means onto said display screen and to traverse a line of impingement.

`2. The invention defined in claim 1, wherein said apertures are constituted by conductive cylindrical members affixed to each plate.

3. The invention defined in claim 1, wherein said multibeam electron gun as-sembly is aimed at a direction greater than but less than 210 with respect to said display screen.

4. The invention defined in claim 1, wherein said means for deflecting includes deflection electrodes oriented so that any defiection field established between them is substantially normal -to the plane of said display screen and wherein said multi-beam electron gun is aimed at a direction toward said -the rear wall of said tube and away from said display screen.

5. The invention defined in claim 1, wherein said display screen is positioned such that it -is viewed from -the surface thereof impinged upon by the electron beams.

`t5. The invention dencd in claim 1, including at least one further of said multi-beam electron gun along another side of said display screen,

said display screen being constituted of a plurality of multifaceted protuberances, with at least one facet facing in a direction to be impinged upon by `only one beam from one of said multi-beam sources and at least one facet facing in a direction to be impinged upon by only one beam from the other of said multibeam sources,

'and each of said facets facing a multi-beam source having a different color producing phosphor thereon.

7. In a flat multi-beam display tube having a display screen, an integral focusing and acceleration electrode structure for ea-ch beam, comprising,

an elongated mul-ti-electron beam source,

a first elongated conductive planar member having a .plurality of passages therein each such passage being aligned with one of the beams from said multi-beam source, respectively,

a second elongated conductive planar member having a plurality of passages therein corresponding in number to the number of passages in said first conductive planar member, each passage in said second conductive planar member being coaxially aligned with a corresponding passage in said first conductive planar member,

means mounting said conductive planar members `in spaced apart relation with respect to each other and said multi-beam source,

means applying a fixed high electron beam accelerat- -ing voltage to the second of said planar members with respect to said source,

means for applying a variable lower po-tential to said first conductive planar member,

whereby a variable converging electrostatic beam focusing lens is formed for each individual beam of said multi-beam source between surfaces of said aligned passages, respectively, and ya substantially uniform acceleration force is applied to all beams exiting from passages in said second conductive planar member.

8. The invention defined in claim 7, wherein said passages are constituted by conductive tube members secured to said conductive planar members.

9. The invention defined in claim 7, wherein said elongated multi-beam source includes an elongated heated cathode member capable of emitting electrons along its length,

`a plurality of grid wires transverse to the long dimension of said elongated cathode,

means for applying to each of said grid wires, individually, a beam control and switching potential,

a planar conductive member commonly spaced from all of said grid wires, and

means for applying `intensity modulating potentials to the last named planar conductive member.

10. The invention deiined in claim 7, wherein said display screen is positioned such that it is viewed from lthe surface thereof impinged upon by the electron beams.

11. The invention defined in claim 7, wherein said means mounting saiid conductive planar members in spaced apart relation includes a nonconductive substrate, one of said conductive planar members being on one side of `said nonconductive substra-te and the other of said conductive planar members being on the other side of said nonconduc-tive substrate, said substrate having electron passage means therein.

12. The invention defined in claim 11, wherein said conductive planar members .are constituted by conductive platings on said nonconductive substrate, said passages being constituted by plating o-n walls of apertures formed in said substrate transverse to Ithe surfaces of said nonconductive substrate.

13. The invention defined in claim 7, including means for establishing a beam dee-ction field normal to said display screen, said second conductive planar member being oriented with respect to said de-ection field such that electron beam-s exiting from apertures in said second conductive member, if undeflected, travel in a direction away from said display screen.

14. The invention defined in claim 13, wherein any electron beam exiting from said second conductive planar member is caused to traverse a plurality of parabolic paths to said display screen each parabolic path being according to the field strength of said deflection eld.

15. A method of producing an image on a display screen in an evacuated fiat envelope having an elongated source of electrons at one -side of said envelope, said elongated source of electrons having a length at least equal to one length dimension of the image to be produced on said display screen, comprising the steps of:

permitting electron emission from said source from a first selected point along its length for a predetermined period of time and preventing electron emission from other selected points along the length of said source during sadi predetermined period of time,

intensity modulating said electron emission from said first selected point,

simultaneously accelerating and focusing the beam elctrons emitted from said first selected point, deliecting said beam of electrons emitted from said first selected point to impinge upon said display screen along a line of impingement, sequentially terminating emission from said selected point and initiating emission from another selected point on said elongated cathode, and modulating, accelerating, focusing, and deflecting each succeeding beam whereby a plurality of lines of impingement are traversed on said display screen, ea-ch line of impingement being traversed by one of said beams emitted from a selected point on said elongated source, respectively.

16. The method defined in claim 15, wherein said display screen is positioned with respect to paths of said beams that the surface of said display screen is impinged upon by said beams is the screen viewing surface seen by an observer.

17. 'Ihe method defined in claim 15, wherein said steps of deflecting includes establishing a plurality of deflection fields, each in sequence, and each being oriented in a direction normal to the plane of said display screen.

y18. The method defined in claim 15, wherein t-he steps of deecting a beam includes,

establishing a deflecting field having a direction normal to said display screen,

the steps of permitting electron emission, simultaneous `accelerating and focusing, include aiming beams from selected points in a direction greater than but less than 210 to the direction of said deliect- `ing field.

19. The invention defined in cl-aim 18, wherein said display screen is positioned with respect to paths of said beams that the surface of said display screen impinged upon by said beams is the screen viewing surface seen by an observer.

20. The invention defined in claim 18, including the step of establishing a fixed electrical guiding field for guiding deflected beams to substantially uniform angles of impingement on said display screen.

References Cited UNITED STATES PATENTS 2,449,339 9/ 1948 Sziklai 315-13 12,795,731 6/ 1957 Aiken. 2,858,464 10/ 1958 Roberts. 2,904,722 9/1959 Aiken. 3,176,184 3/1965 Hopkins 315-13 `5,226,596 12/1965 Kasperowicz.

RICHARD A. FARLEY, Primary Examiner M. F. HUBLER, Auxiliary Examiner