US3852634A

US3852634A - Switch device for point selector electrodes in flat television screens

Info

Publication number: US3852634A
Application number: US00331443A
Authority: US
Inventors: L Sullos
Original assignee: Individual
Current assignee: Individual
Priority date: 1972-02-17
Filing date: 1973-02-12
Publication date: 1974-12-03
Anticipated expiration: 1991-12-03
Also published as: JPS4895172A; DE2306823A1

Abstract

This invention provides a switching device for point selector electrodes in flat television screens comprising horizontal and vertical electrodes, able to vary progressively the potential of said electrodes in order to scan an image, characterized in comprising an electron emissive cathode with focusing electrodes able to obtain an electron beam having a cross-section at least 10 times longer than wide; at least one electrical resistance in the shape of an elongated bar having a length at least equal to that of said focusing electrodes and arranged parallel to the outlet opening (of the electron beam) provided on the said electrodes.

Description

United States Patent 1191 Sullos SWITCH DEVICE FOR POINT SELECTOR ELECTRODES IN FLAT TELEVISION SCREENS Inventor:

[76] Ludwig Sullos, Acevedo 1439,

Banfield, Buenos Aires, Argentina Filed: Feb. 12, 1973 Appl. No.: 331,443

[30] Foreign Application Priority Data Feb. 17, 1972 Argentina 240578 U.S. Cl 313/422, 313/432,-313/105 Field of Search 313/82 NC, 78; 315/3 References Cited UNITED STATES PATENTS 11/1939 Barthelemy.. 315/8 9/1948 SZiklai 313/78 X Int. Cl H0lj 29/74, HOlj 29/56 1 Dec. 3, 1974 6/1959 Van Doorn et 111...... 3l3/78 x 5/1973 Buck 315/3 Primary Examiner-Robert Segal Attorney, Agent, or FirmLadas, Parry, Von Gehr, Goldsmith & Deschamps [5 7] ABSTRACT 5 arranged parallel to the outlet opening (of the electron beam) provided on the said electrodes.

2 Claims, 2 Drawing Figures PATENTEL BEE 3 74 SWITCH DEVICE FOR POINT SELECTOR ELECTRODES IN FLAT TELEVISION SCREENS This invention is related to a deflection device for flat imaging screens. More particularly, it is related to flat television screens comprising a flat photocathode of a size similar to that of the image; a control grid system printed on a polyethylene body operating as point selectors horizontallyv and vertically arranged grids and color selectors, the latter being able to produce a postdeflection and to cause the current controlled thereby to activate a colored mosaic conveniently provided for obtaining the three primary colors. To return to the point selector grids, the instant device is applicable to energizing said grids in series and at a speed required by the vertical and horizontal scanning sweepings. v

Similar devices are known which operate using a photocathode and secondary emission multiplier electrodes; they operate so that each grid has an associated circuit providing the voltage changes required by said grid and causing that when a grid returns to an unenergized condition, the following grid is energized. This is achieved by means of resistors and capacitors coupling the circuit of one grid to the following. Moreover, the return of a grid to an unenerg ized condition and the energization of the following grid are controlled by an external circuit an oscillator assuring the uniformity of the energization intervals. Such devices assure an excellent linearity, but their principal drawback is caused by the complexity in the production of the coupling circuit between the grids, inasmuch as if there are 700 grids, the same number of coupling circuits is required, and each of them may comprise a condensor and various resistances and. including control electrodes on the photocathode portion corresponding to the same or the adjacent grid.

The instant device eliminates all the coupling elements between adjacent grids and as willbe seen later reduces considerably the production cost of the flat screen while increasing its operational stability.

FIG. I is a sectional view through a bar in which the point selector grids terminate, and FIG. 2, in its top portion, shows the selector grids as a grate with the respectivebars wherein they begin and terminate. The bottom portion of FIG. 2 is an operational graph which shall be explained later. It is to be assumed that the grate is arranged over an extended photocathode surface (not shown) without touching it, so as to be able to control the current emitted by said surface. In this case, if all the grids are negative 10 volts with respect to the photocathode, no current passes through the grating. If a pair of grids, perpendicular to each other, become positive or at zero potential with regard to the photocathode, and if a positive electrode ,(not shown) is provided on the opposite side, there will The energization of each grid is achieved as'follows: the grids are dipped at one of their ends in resistive paste which is represented in FIG. 2 by

details

19 and 25, and in such a way that each grid receive a 10 Kohm resistance with a common electrode. The other ends of the grids terminate in detail 18 of FIG. 2 constituted by respective tabs each with a-surface prepared so as to have a high secondary emission for changing the potential of the associated grid in response to electron beam impingement of the surface. One of these surfaces is illustrated in FIG. 1 at 9, with 14 being the reference number of the polyethylene body serving as its base. This electrode is energized by V electrons and an efficiency factor 4 emission is produced; the energizing current is l mA and the emitted current is 4 mA, meaning that for the 10 Kohm resistorof the corresponding grid 3 mA will circulate and cause the potential of said grid to vary towards a more positive value. This effect should be achieved in such a way that theenergizing area be transferred from tab to tab at the required speed. In FIG. 2, 15, 16 and 17 constitute the device used to achieve this end. 15 is a photocathode and a focusing system producing a long and narrow electron ing the same length is provided for dissipating the heat generated by resistance 5. Number 17 in FIG. 2 indicates the electron multiplying system which in FIG. 1

is represented in perpendicular section by elements 7, jointly with element 8 which is the'terminal collector anode, shaped as a thick copper bar the purpose of which is to dissipate the heat. FIG. 1 is a section through the deflection device at any point of a perpendicular plane,except details 9 and 14 which pertain to the plastic sheet carrying the point selector grids. This device is comprised solely by parallel bars, mounted in plastic 13 and does not contain specific details corresponding to individual grids. Number 10 is aphotocathode surface, and 11 is a luminous phosphor coated electrode constituting a regenerative photocell, with the sole purpose of illuminating photocathode 1 with a light having a given value in the order of 1000 lux inasmuch as the electron emission from 1, on its entire surface, should not be in excess of 60 uA. Electrode'2 has the same potential asl, electrode 3 has a potential in the order of 5 20 V; 4 is a focusing electrode adjustable for obtaining the narrowest possible beam. 5 is a long resistor, made of a paste very uniform as to its resistive characteristics, the purpose of which is to deflect the beam as obtained to one side or the other, enabling the electrons to enter the multiplier enclosure only in the area where said resistor has the same potential as electrode 3; this resistor, whose input terminals are 26 and 27 FIG. 2 has an end to end or terminal to terminal value of 250 -.800 Kohm to minimize the current flow therein; the values comprised between the said extremes are optimal. Electrode 6, at a potential in the order of 40 200 V is a beam director permitting the electrons to arrive at the most appropriate portion of 7; 7 is a secondary emission multiplier electrode the same as the remaining similarly shaped electrodes following in line. In the experimental tests pitches of 300 or 400 V were used in order to obtain factors in the order of the 6s and to cause the last electrode 7 to emit 1 mA.

The operation is simple. In the first tests, resistor S was at 500 Kohm and between

terminals

26 and 27 350 V were applied. Thereafter, by energizing both ends with a saw-tooth voltage, the transfer of the point where the potential of resistor is equal to that of focusing electrode 3 was achieved, and therewith the transfer of a narrow beam energizing surfaces 9 of the tabs 18. The bottom portion of FIG. 2 is a diagrammatic illustration of the voltages appearing on resistance 5. The energization of said resistance must be such as to provide at any time a voltage of 350 V between its ends. For instance, on line 21, at the left end the voltage is zero and at the right end, 350 volt. Straight line 22 shows what happens when all the points of resistance 5 vary by 200 volt; it is noted that although the voltage distribution has not varied with regard to the ends, it has varied with regard to the zero volt line. This is achieved by applying the same voltage variations to both ends of resistance 5. The other extreme position is the one shown on line 23, where the left end is at 350 volt and the right end at zero volt. Between the conditions illustrated by 21 and 23, it is possible to pass through all the intermediate positions, i.e., by causing the points of the lines to correspond with the points of resistor 5, it is possible for each point to pass at a given moment through the zero volt line. If said line is the one representing the potential of electrode 3 and if both ends of resistor 5 are energized with the same saw-tooth voltage, the point at zero volt will sweep during each cycle the entire resistor. On the other hand, zero volt point is where the beam formed by electrodes 1, 2, 3 and 4 may enter the hole in electrode 3 and reach the secondary emission electrodes. The width of the entering beam is the smaller, the larger is the continuous potential between the terminals of 5. With 350 V a width below 1 mm was obtained. The current reaching the multiplier electrodes is in the order of 0.1 microamper; it varies withthe variation of the focusing electrodes, however it is possible to obtain it as narrow as the minimum detail of the image on the screen. In practice, a drawback was encountered: for instance, inthe case of line 22, the entire portion of 5 which is at a positive potential with regard to 3 absorbs the current emitted by photocathode 1, while the remaining portion does not absorb beam current, repel ling the beam so as to be absorbed by electrode 3. This current absorbed by 3 produces a deformation of the linearity, inasmuch as it alters the potentials of 5 by displacing the zero volt point. Said current is in the order of 60 p.A. With 5 at 500 Kohm and 350 V between the terminals, the continuous current by 5 is of 700 uA. This means that the 60 [LA constitute less than percent of the total, thus causing a nonlinearity in the same order. In practice, this drawback has been solved by altering the shape of the sawtooth wave energizing both terminals of 5; by means of R-C-circuits, a linearity in the order of 2 percent was achieved at the first try; i.e., the disturbing effect of the current absorbed by 5 can be obviated by circuit arrangements outside the screen. Copper bar 12 became unnecessary, inasmuch as the heat dissipation of 5 amounted to 250 mW. And as the physical dimensions of 5 were those of an 8 X 8 mm by 500 mm length bar, the heating was negligible. As to the tab 18, the heat dissipation may pose a problem if the sweeping were detained at an intermediate point of the screen. The last secondary emission multiplier electrode 7 emits l mA. Tab 18 in FIG. 2, and surface 9 in FIG. 1 are at 120 V with regard to the above mentioned electrode and through secondary emission emits 4 mA which are absorbed by electrode 8 which is at 50 100 V with regard to 9. 8 is a thick copper bar and obviates the heating problem, inasmuch as it must dissipate merely 400 mW. However, surface 9 is a plate 0,7 mm wide not more than 6 mm long. The remainder penetrates into the screen acting as a point selector. The plate receiving 1 mA at l20 V, that is having to dissipate l2O mW, becomes very hot if the beam is detained; in practical experience, the assembly of sur faces 9, totalling 300 surfaces, each having a width of 1 mm, was mounted in the form of a circuit printed on a phenol-formaldehyde plastic material reinforced with amiantus fiber which was appropriately positioned with regard to electrode 8. We shall refrain from describing the manner in which the dynamic voltages on each surface 9 were taken, as such a description would be very extensive and unrelated to the main object of this patent. The plastic material did not vary with I20 mW, however due to the impurities existing between the copper and its base, as the current and the dissipation increased, the sheet peeled away from its base and the appearance of gases made a repetition of the high vacuum procedure necessary. In another experience, the tabs were mounted on a thick copper bar, separated by a 0.2 mm thick chemically settable adhesive layer; in this new arrangement the heating problem was solved. This means that if due to a breakdown of the deflection voltage generator the energized point were detained, the screen would not deteriorate. Another reason for nonlinearity which appeared with sawteeth in excess of l0 Kc/sec was the capacity distributed by resistance 5. This was obviated with an appropriate modification of the saw-tooth exciter through R-C loops. For frequencies of 50 cycles per second the distributed capacity posed no problems. For the illumination of photocathode 1 an arrangement of elements already described see FIG. 1 was used, based on a regenerative photocell. Photocathode 10 emits electrons and surface 11 is a transparent conductor coated with type P4 phosphor. Due to deficiencies in the deposition, the critical voltage was in the order of 4 KV. The current was limited by means of a resistance in series; by regulating the value of said resistance it was possible to vary the light energizing the photocathode l and its emission, limiting the same to uA as total current. In a later test, by the application of 600 V pitches between multiplier electrodes, an emission of 1 mA was achieved in the last electrode 7, with a total emission from photocathode 1 not in excess of IO A; with the latter, it was possible to obviate the circuit for the correction of linearity through absorption of the current from resistor 5, inasmuch as the nonlinearity produced by the absorbed current is as low as 1.4 percent at the edge of the screen.

FIG. 2 is a diagrammatic illustration of a point selector device with a matrix of horizontal and vertical grids. Detail 20 corresponds to the beam generating focusing, deflecting and electron multiplying devices associated with tabs 18 and the vertical grids; 24 are the corresponding tabs, fulfilling the same purpose as tabs 18; 25 is the compact bar of resistive paste in which terminate the horizontal grids. Neither the flat luminescent imaging screen not the flat photoemissive surface I whose emitted electrons may be controlled by the matrix to impinge point by point on the screen are shown;

To resume, it is stressed that in the flat screen with 600 horizontal and 700 vertical grids, measuring 36 X 47 cm, there is a total of 1,300,000 points as each grid is able to control two image points which is by far in excess of the present requirements of television. The reduction in the number of grids there can be 300 and 350 simplifies the production. The color selector plates, which are applicable to the screen as described and which are comprised of deflector grids and multiplier plates, allow the obtention of flat color television screens compatible with systems of up to 400,000 points, the production cost being in the long run very similar to that of the present black andwhite receivers, but of a quality indisputably superior to that of any of the known color systems.

Having thus described and determined the nature and scope of the'present invention and the manner in which the same is to be put into practice, it is hereby stated that what is claimed as invention and exclusive property is: e

l; Deflection apparatus for flat imaging screens, comprising in combination:

a. a cathode and focusing electrodes for generating a flat electron beam having a width substantially equal to that of the image to be produced, two deflecting electrodes positioned on opposite sides of the path of said flat beam and in parallel relationship to said focusing electrodes, one of said deflecting electrodes being of resistive material and havhaving a slit parallel to said deflecting electrodes;

b. multiplier electrodes having a length substantially the same as that of said deflecting electrodes and being disposed in parallel relationship to said slit, said multiplier electrodes being followed by a terminal collector anode of the same length;

c. a row of tabs disposed in parallel relationship to said multiplier electrodes and having respective secondary emission surfaces in position be be impinged successively by said flat electron beam as the beam is narrowed and undergoes deflection in the direction of said row under the influence of said deflecting electrodes, each tab being electrically connected to one end of a respective one of a plurality of image control grids arranged in a common planewithout touching each other and lying perpendicular to said row, the opposite ends of said image control grids being coupled by way of resistive means to a common terminal; and,

. a duplication of (a), (b) and (c) wherein the common planes of the two pluralities of image control grids are adjacent and parallel, with said pluralities being mutually perpendicular to form a matrix of image control grids, said matrix beingadapted to be disposed in non-contacting relationship to and between transparent photoluminescent and photoemissive plane parallel surfaces equal in size to that of the image to be produced so as to control the impingement of electrons emitted from the photoemissive surface upon the photoluminescent surface. v

2, Apparatus according to claim 1, wherein said terminal collector anode is a metal bar electrically insulated from said tabs and positioned to dissipate heat developed in said tabsby impingement of the. electron beam thereon.

Claims

1. Deflection apparatus for flat imaging screens, comprising in combination: a. a cathode and focusing electrodes for generating a flat electron beam having a width substantially equal to that of the image to be produced, two deflecting electrodes positioned on opposite sides of the path of said flat beam and in parallel relationship to said focusing electrodes, one of said deflecting electrodes being of resistive material and having two terminals by which current may be applied through said one deflecting electrode to flow in a direction perpendicular to the electron flow in said flat electron beam, and an electrode disposed in parallel relationship to said deflecting electrodes on the side thereof remote from said cathode and having a slit parallel to said deflecting electrodes; b. multiplier electrodes having a length substantially the same as that of said deflecting electrodes and being disposed in parallel relationship to said slit, said multiplier electrodes being followed by a terminal collector anode of the same length; c. a row of tabs disposed in parallel relationship to said multiplier electrodes and having respective secondary emission surfaces in position be be impinged successively by said flat electron beam as the beam is narrowed and undergoes deflection in the direction of said row under the influence of said deflecting electrodes, each tab being electrically connected to one end of a respective one of a plurality of image control grids arranged in a common plane without touching each other and lying perpendicular to said row, the opposite ends of said image control grids being coupled by way of resistive means to a common terminal; and, d. a duplication of (a), (b) and (c) wherein the common planes of the two pluralities of image control grids are adjacent and parallel, with said pluralities being mutually perpendicular to form a matrix of image control grids, said matrix being adapted to be disposed in non-contacting relationship to and between transparent photoluminescent and photoemissive plane parallel surfaces equal in size to that of the image to be produced so as to control the impingement of electrons emitted from the photoemissive surface upon the photoluminescent surface.

2. Apparatus according to claim 1, wherein said terminal collector anode is a metal bar electrically insulated from said tabs and positioned to dissipate heat developed in said tabs by impingement of the electron beam thereon.