US2769115A - Method and means for producing high degree television picture brilliance - Google Patents

Description

R. J- CALLENDER METHOD AND MEANS FOR PRODUCING HIGH DEGREE Oct. 30, 1956 ELEVISION PICTURE BRILLIANCE Filed Aug. 20, 1951 KB; QQQSW 23 QQQWN Ru 8%? ES; his: QQIL o E QQEN E Q3 3 E E uh? 3ft E 93 o v A INVENTOR Russell J; C'a/lendzr United METHOD AND NIEANS FOR PRODUCING HIGH DEGREE TELEVISION PICTURE BRILLIANCE Russell J. Callender, St. Paul, Minn.

Application August 20, 1951 Serial No. 242,671 12 Claims. (Cl. 3151-14) a high degree of picture brilliance without the concomitant disadvantage of rapid deterioriation of the cathode ray tubes luminescent screen, such deterioration being commonly referred to as burning or browning. In this connection, I have found it possible to increase the brilliance of a cathode ray tube by as much as 50 to 100% without noticeable browning of the screen during the expected life of the tube.

A further object of the invention is to produce a focusing and electron accelerating arrangement wherein the electron beam stays in focus over a wider angle of beam swing. In other words, I obtain excellent focusing at the fringe of the picture. In this connection, it is also to be noted that my system stays in focus under wide fluctuations of anode voltages caused by large changes in beam current.

A still further purpose of the invention resides in the provision of a cathode ray tube that is no more complex than tubes now in general use, and which can be sold at approximately the same price.

Another object of the invention is to provide a cathode ray tube and associated apparatus suitable for installation in existing television sets with little adaptation thereof.

Still another object of the invention is to obtain a perfect beam current cut-off, thereby producing an improved picture contrast.

It is also within the purview of this invention to obtain a better utilization of the electrons emitted fromthe cathode.

With the foregoing and other objects in view, which will be manifest in the following detailed description and specifically pointed out in the appended claims, reference is had to the accompanying drawings for an illustrative embodiment of the invention wherein:

Figure 1 is a schematic representation of a cathode ray tube and associated details presented in elementary form in order to" provide an understanding of the basic concepts involved in the invention; and

v l-Tigure '2 is an end viewof the screen of the tube depicted in Figure l, a conventional picture area being shown in dotted outline and my recommended increased picture areabeing shown in dash outline.

Referring now to the drawing, there is shown a cathode ray tube A adapted for use in the practicing of my invena heater filament 12 at one end which is in heat transfer relationship with a cathode 14. The flow ofelectrons 2,769,115 Patented Oct. 30, 1956 derivative 18 of the television signal being transmitted.

- Axially positioned wtih respect to the control grid 16 is tionl; The tube A includes a glass envelope 10 having emitted by the cathode 14 is first controlled or regulated by-a control grid '16 containing in circuit therewith a a first anode 20 provided with a flared end 22. A second anode 24 is disposed beyond the anode 20, this anode 24 being generally cylindrical and containing therein a plurality of annular elements 26. A conductive coating 28, such as Aquadag, serves as a third anode, the coating being applied to the inner surface of the glass envelope 10. It will be observed from the drawing that the coating 28 is cylindrical adjacent the end toward the second anode 24, belling outwardly into conductive relationship with a luminescent screen 30 applied to the large end of the envelope 10. For purposes well understood in the Kinescope art, the screen is preferably aluminized on its inner surface.

Outwardly of the neck of the envelope 10 is circumposed a magnet element 32 which may be a permanent magnet, an electromagnet, or a combination electronpermanent magnet. The magnet 32 may be circumscribed about an insulating carrier sleeve 33 which is in sliding engagement with the envelope 10. In this way the sleeve 33 may be moved axially with respect to the envelope 10 to produce an optimum focus of the electron beam being accelerated by the anodes 24 and 28. In order to obtain the proper physical center of the electron beam as it strikes the screen 30, I provide an annular steel element 34 having a bore 35 of larger diameter than the outer diameter of the envelope 10. It will be apparent that the attraction of the magnet 32 will retain the annular steel element 34 in the desired position, such position once having been obtained by adjustment of said annulus in a plane normal to the general axis of the envelope 10.

The invention envisages the employment of hori zontal and vertical magnetic deflection coils 36. and 37 which operate in a known manner to produce the desired scanning of the electron beam over the surface of the screen 30. As is customary in television receiving sets, the coils 36 and 37 may be provided with inductive shunts by which the magnetic field intensity of the coils may be varied. Later on it will be explained that the coils 36 and 37 are adjusted to produce a magnetic field of such intensity as to partiallydefle-ct the electron beam off the luminescent screen 30.

For the purposes of simplicity the means for pro- The potentiometer B is grounded at 38; thereby affording a negative bias of from to volts at39, such a 5 negative bias when applied to the control grid. 16 and influenced by the incoming signal 18 producing the neces-;

sary change in electron emission to therebyprovide an electron beam of the proper intensity variant. The cathode 14 is connected to the potentiometer at 40 which point is at an approximate potential "level of 25 volts.

The first anode 20 is adjustable over a range of from approximately to 300 volts, as indicated by its potentiometer connection at 42; In practice, the potential of;

the anode 20 is adjusted for beam cut-off, or proper black picture level for the no signal bias of the'control grid- 16. The anodes 24 and 28 are connected to the potentiometer at Mand 45 to provide accelerating potentials of. 12,000 to 15,000 volts and 27,000 to 31,000 volts,

respectively. In order to properly insulate the anode lead 46', which passes through the glass envelope 10,1 preferv In operation, the tube elements 14, 15, 20,24 and'iii are adjusted to the proper Voltage values, the specific values and ranges thereof given above being typical for a representative application, As previously mentioned, it

will be noted that the potential of the anode such a as to provide beam current cut-off when so signal is being received. With the. tube A thus placed in operation, the coils 36 and 37 are adjusted to a field strength such as to swing the-electron beam through a greater spherical angle than is normally done. For example, the normal area 7 coveredby the scanning beam is representedby the dotted rectangle 48, While the increased area subtended by the greater spherical angle of electron project-ion is designated by the numeral'Si). It Will'be apparent from Figure 2 that certain e t-rerneportions of the produced image are lost in that the electron beam will strike sections of the tube A which are either not coated with fluorescent matenial or whichare on the sides of the tube head and therefore not directly visible from a position confronting the screen 30. 7

After setting the beam in scanning'motion, as above outlined, the magnetic element 36 is moved into the best focusing relationship obtainable. Asa general rule, the magnet 32 is moved toward the screen 30 when relatively large electron accelerating voltagesare employed and in the opposite direction when smaller voltages are utilized.

i third anode elements, and beam deflecting means,

The magnet 32 therefore should be designed for the field V strength that will give the most optimum focusing effect.

However, it will be appreciated that fora magnet having 7 a particular field strength, the voltage impressed upon the anode 24 may be changed to provide similar focus- -ing. But since a'change of the voltage of the. anode 24 influences the brilliancy of the, image on the screen30, it

is preferable to adjust the potentialof the anode 24 for the desired brilliancy, and to select a'magnet of the proper strength for the 'potentialused." By employing a combined permanent and electro-rnagnet'element, the strength of the magnet 32 may be adjusted to likewise produce the a focus. Also, if desired, after selection of the voltage at, the anode 24, the focusing. may be obtained by increasing,

the length of magnetic path throughwhich the electrons good focusing adjacent the fringe areas of, the picture, but at the sametimeit eliminates the need fora cooling fan,

must flow by adding magnetic rings to the magnet; 32; Y

usually required in large picture projection, while pro- 7 longing the usable life of the cathode ray tube.

In accordance with the patent statute's, I have described the principles of construction and operation of my method and means for producing high, degree, television picture brilliance, and while I havexendeavored to set forth th'e best embodiment thereof, I desire to have it understood that obvious changes may be'made within the scope of the following claims without departing-from the spirit of my invention. r

.Iclaimz 1. In combination withia television receiver, a cathode ray tube comprising a cathode 'ele'mcnna control grid element,=first,' second and third cylinder anodeelements in straight gun alignment'andelectrostatic and magnetic V field fofcusingmeans circumscribingjthe second anode element, said several anode elements being of progressively.

I greater potentials with respect to said cathode element.

2. In a television receiver, a cathode ray tube comprising in combination a cathode element, a controlgrid element, a first anodeele ment having a potential applied.

thereto for biasing theelectron beam to cut-off, asecond anodeelernent havinga potential of fromabo ut 12,000

toabout 15,000 voltsapplied thereto, a third anode element having a potential of from about 27,000 to about 31,000 volts applied thereto, magnetic means circumjacent said second anode element, for focusing the electron beam, and magnetic deflecting coils. having suflicient field strength to deflect said beam beyond'the'normal viewing limits of the cathode tube screen, whereby the refractive: power of thersecond electrodeaccomplishes focus of the electron beamelectrostatically and magneticthe method comprising the steps of subjecting the third anodeelement to a'relatively high operating potential, the second anode element to an intermediate potential and the first anodeelement'to a relatively low potentialeach' of said steps progressively increasing the velocity of an electron beam from said first to said third anode elements,

said relatively low potential being suflicient to biasth'e cathode ray tube beam to cut-off, and focusing thercathode ray tube beam adjacent the locus of the second anode-element to produce a well defined image on the screen of said tube.

4. The method'ofsclairn 3 in which the second "anode element is subjected to a potential approximating onehalf' of the potential applied to said third anode element.

5. The method of claim 3 in which the beam deflecting means is adjusted to a strength which will deflect the beam into a region beyond the viewable limits. of. the

tube screen, thereby producing a picture containing only the more central portion of the televised image. 1

-6 A method of producing an enlarged televised'image having a high degree of picture brilliance which includes.

accelerating an electron beam at one potential, then to a greater potential and then to a still greater potential, and creating electrostatic and magnetic refracting fields to focus said electronbearn on a fluorescent screen without changing the length of the focal distance and said last "mentioned potential providing increased acceleration to said electron'beam to produce a wel defined image onsaid fluorescent screen. without noticeable burning or browning the screen.

V 7. A method of producingfarelatively enlarged. and brilliant television picture whichjcomprises the steps of I 7 increasing and accelerating the velocity of an electron beam through several stages including an intermediate stage, controlling the negative ions of the said beam at said intermediate stage to avoid browning of the picture 1 screen by the increasedvelocity of the'said beam, focusing Y the said beam adjacent one ofsaid intermediate stage, and deflecting said beam beyond the normal viewing limitsof a luminescent screen to thereby prevent said'electron beam from'striking the screen adjacent the marginal porp tionsof the complete picture being televised by the transmitting station.

' vided with an enlarged public viewing screen upon which .a picture is. obtained with a. high degree offlbrilliance.

without noticeable burning or browningeqf the :screen; during the lifelof the tube, said cathode ray tubehaving a cathode element, a control grid ele'menha series of; spaced anode elements forgsteppingupthevoltage-onihe, order of from volts toIlOOvoltsiatthe cathode to the-f I'order of;.27,000 volts to 31,000 volts at-the screen, one. :ofsaid anode elements positionedin aligned intermediate 8. In combinationpa televisionreceiving systemprorelationshiprto the other'of the anode elements and care rying a voltage on; the order of 12,000 voltsto' 1' 5,00 0 volts in the said series, tanfaxially adjustable magnetic, focusing element aboutsaid 'tube lcircumscribing said. 7 intermediate; anode,- an insulation. mounting for said magw; netic'focusing element, and a deflection yoke cooperative a 1y producing an optimum focus of the election beam being accelerated toward said screen by said intermediate anode and another anode in spaced relationship thereto adjacent said screen.

9. The structure of claim 8 wherein the said anode between said intermediate anode and said screen is in conductive relationship with said screen and connected to an insulated lead in.

10. The structure of claim 9 wherein the magnetic focusing element is a combined adjustable permanent and eleetromagnet means.

11. In combination with a picture screen viewing television cathode ray tube having a cathode element, a control grid element, a plurality of special aligned anode elements of progressively greater potentials with respect to said cathode to produce an accelerated election stream, a magnetic focusing element circumscrioing an anode element in said alignment in spaced relationship to an anode adjacent said picture screen, a deflection yoke, and an insulation enveloping said tube adjacent the region of the screen to prevent are over therefrom of the accelerated high voltage.

12. The structure of claim 11 including a third anode enclosed by said insulation and said tube and an anode lead-in which passes through the said insulation and into said television tube.

References Cited in the file of this patent UNITED STATES PATENTS

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