US2930930A - Electronic device - Google Patents

Description

lMmh 29, 1960 w R. AIKEN ELECTRONIC DEVICE 3 Sheets-Sheet 1 Filed Mair 5, 1957 INVENTOR William Russ Aiken ATTORNEY March 29, 1960 w. R. A|KEN ELECTRONIC DEVICE 3 Sheets-Sheet 2 Filed )lay 3. 1957 WPI;

f f f f E f INVENTOR William Ross Alken 2... om ovofoo 'Much 29, 1960 w. R. AIKEN 2,930,930

ELECTRONIC DEVICE Filed Illy 3, 1957 3 Sheets-Sheet 3 ATTORNEY United States Patent O ELECTRONIC DEVICE William R. Aiken, Los Altos, Calif., assigner, by mesne assignments, to Kaiser Industries Corporation, a corporation of Nevada Application May 3, 1957, Serial No. 656,874

1 3 Claims. (Cl. 315-13) The present invention relates to cathode ray display tubes and more particularly to thin cathode ray tubes capable of polychromatic displays utilizing the deflection principles described in applicants copending application Serial Number 396,120, filed December 4, 1953, now Patent No. 2,795,731.

In the prior art, it has been proposed to display the television image signal by means of cathode ray tube using one or more electron guns adapted to deliver electrons toward a target screen of discrete sensitized areas of electron sensitive fluorescent materials being capable of emitting light of the desired color component elements such as red, blue, and green upon excitation by electron bombardment. These sensitized areas have assumed a variety of configurations such as dots, lines, and pyramids. Yarious combinations have been proposed to provide means for scanning the target screen in accordance with the scan of the transmitted object, and for modulating, controlling, and orienting the electron beam to produce the desired luminous color and to limit the impingement thereof to only the desired sensitized area. The electron beam or beams may be caused to scan the three primary color light emitting areas in sequence or simultaneously so that the luminosity of the three color values are additive to the human eye to thereby reproduce the hue and saturation of the particular color signal or to produce the conventional black and white image areas. Numerous systems and structures have been proposed to control and modulate the electron beam so as to thereby produce the desired scanning of the sensitized areas and to prevent the impingement of the electron beam, or any portion thereof, upon undesired color sensitized areas. The display arrangements proposed by the prior art include many relatively complicated and expensive dellecting grid and masking arrangements which are designed to limit the impingement of the electron beam on only the desired primary color area.

Other attempts have been made to produce color kinescopes employing a single gun wherein a plurality of phosphors capable of emitting light of different colors are settled on the target screen in discrete layers. The layer to be excited is determined by adjusting the beam energy to obtain the appropriate depth of penetration of the composite screen. Manifestly, to effect the maximum degree of penetration, the application of extremely high voltages would be required during which time correspondingly high voltages must be used to effect the desired scanning of the electron beam across the target screen. The electronic circuitry used for switching colors, that is the degree of penetration of the beam into the target, is necessarily extremely complex.

An object of the present invention is to produce a cathode ray tube having a target screen comprised of a plurality of phosphor layers wherein the layer to be excited is determined by the depth of penetration of the beam which is controlled by the angle with which the beam impinges the target.

Another object of the invention is to produce a cath- -2,930,930 Patented Mar. 29, 1960 ICC ode ray tube capable of exhibiting polychromatic displays which has a minimum number of components lending the structure to economical manufacture and operation.

A further object of the invention is to produce a polychromatic cathode ray tube having' a relatively small depth dimension as compared with its length and width.

Still another object of the invention is'to produce a cathode ray tube having a layered target with a common deflection set for all color which results in superposed dot registration.

In accordance with one embodiment of the invention, the cathode ray tube comprises a target screen composed of three color phosphors settled thereon in separate layers. A source consisting of an electron gun, or alternatively a plurality of separate guns, is adapted to deliver three parallel beams of electrons along a marginal edge of the target. For purposes of simplicity, the specific disclosure hereinafter relates to the manner in which a tube having three separate guns provides three parallel beams to effect selective excitation of the different phosphor layers, it being apparent to parties skilled in the art as to the manner in which a single beam may be adjusted to three like parallel paths with conventional electron beam gun deflection arrangements. A linear set of primary deflection electrodes, which is used to selectively deflect the beam to a zone adjacent the surface of the target, is positioned in adjacent spaced relation with respect to the marginal edge of the target along which the beams are initially delivered. A set of secondary deflection electrodes adapted to selectively deflect the beams into registration with the target is provided adjacent the surface of the target and spaced therefrom an amount sufficient to permit passage of the electron beams therebetween. In this arrangement, it will be understood that when the beams are deflected by the primary electrodes to the zone between the target screen and the secondary deflection set, the relative dispositions of the beam paths is such that each is a different distance away from the target screen.

Energization of the secondary deflection electrodes causes the beams to be selectively deflected into registration with the target. Inasmuch as the beam paths are spaced at different distances from the deflection elements, the deilecting force acting thereon will cause the beams to be deflected through correspondingly different angles. The beams, being of substantially the same energy, each will travel through or penetrate substantially the same distance in the phosphor material of the target screen. However, due to the distinct angles of impingement with the target screen, the individual beams will come to rest in different ones of the color phosphor layers of the target screen. When the beam comes to rest, its energy is utilized to excite the phosphor material of the layer in which it comes to rest. By suitably modulating each of the beams by separate video signals, a polychromatic display may be achieved.

Objects and advantages other than those hereinabove set forth will be apparent to those skilled in the art upon reading the following description in connection with the attached drawings, in which:

Figure 1 is a front elevational view of the cathode ray tube with sections thereof partly broken away to more clearly illustrate the invention,

Figure 2 is a sectional view of the cathode ray tube taken along line 2 2 of Figure 1,

Figure 3 is a schematic illustration of a suitable system employing the instant cathode ray tube for the polychromatic display of television programming.

Figure 4 is an end view of a modified version cathode ray tube shown in Figures l and 2,

Figure 5 is an enlarged end View of a portion of the high voltage section of the tube to illustrate the electron beam penetration into the phosphor material as a result of being deflected through different angles relative to the target,

Figure 6 is an end elevational view shown in section of a modified version of the cathode ray tube illustrated in Figures 1 and 2 specifically showing the employment of a grid assembly adjacent the target, and

Figure 7 is an enlarged sectional view of the modified version of the tube shown in Figure 6 specifically illustrating a means for varying the angles of the beam prior to the instant of impingement onto the target.

There is shown in Figures l and 2, an envelope 10 which is adapted to completely house the internal components of the instant tube and to maintain the desired vacuum therewithin. An electron gun 12 of the type capable of delivering three individual beams of electrons, preferably employing an integral electrostatic deflection system, is disposed within the envelope 10. The gun 12 is adapted to deliver three electron beams 14, 16 and 18 which travel along parallel paths. A linear array of horizontal deflection electrodes 20 is disposed within the envelope 10 along the upper marginal edge thereof. Each of the electrodes 20 is provided within electrical conductor 22 which is adapted to pass through the wall of the envelope 10 in such a manner that vacuum condition will be maintained within the chamber formed by the envelope 10. The array of conductors 22 may be assembled and positioned within a suitable cable means indicated on Figure 3 by reference numeral 24 and in turn connected to a horizontal sweep generator 56 as clearly illustrated in Figure 3.

A slotted accelerating electrode 26 is disposed in spaced and substantial parallel relation with respect to the entire array of deflection electrodes 20. The electrode 26 is suitably energized through a conductor 28 adapted to electrically couple the electrode 26 to a suitable power supply within a television receiver 48 as clearly illustrated in Figure 3. The aforementioned group of components will be referred to hereinafter as the primary section of the tube.

Disposed beneath and extending substantially the entire length of the primary section, there is a pair of focusing and accelerating electrodes 30 provided with a suitable electrical conductor 32 which is adapted to pass through the wall of the envelope 10 to a power supply with the television receiver 48, as clearly shown in Figure 3. The electrodes 30 and any additional similar electrodes which may be included at such point along the beam path will be referred to hereinafter as the transition section of the tube.

The high voltage or secondary section of the tube comprises an electrically conducting transparent panel 34 and an associated set of deflection electrodes 44. The fluorescent coating or target screen is comprised of a plurality of superposed layers 36, 38 and 40 of phosphor material, each of which produces a different colored light upon excitation.

It will be noted that the electrically conducting panel 34 is provided with a conducting wire 42 connected to a source of potential which is positive with respect to the cathode of the gun or guns which provide electron beams 14, 16 and 18. The desired potential is obtained from the power supply within the television receiver 48 shown in Figure 3.

Adjacent and spaced from the composite phosphor target screen comprised of the layers 36, 38 and 40, there is a plurality of deflection electrodes 44 each of which is provided with an electrical conductor 46 adapted to pass through the tube envelope 10 to a vertical sweep generator 58, as shown in Figure 3. The various conductors 46 may be cabled together outside of the tube envelope 10 within a cable 47 as shown diagrammatially in, Figure 3.

In certain applications of the instant tube, it may be deemed necessary to view the display presented on the target screen from each of two sides. In such event, the vertical deflection electrodes 44 are formed of a transparent conducting material, such as for example conducting glass.

Figure 3 illustrates a system employing the instant cathode ray tube in connection with the reception of a television display in color. A standard color receiver circuit may be employed, such as for example RCA Model CTlOO, chassis number CTC2. For purposes of simplification, the above referred to receiver is shown in diagrammatic form by reference numeral 48 and includes a power supply capable of energizing the various components in the instant tube as will hereinafter be set forth in detail.

The horizontal and vertical sweep sync signals are fed to a sync amplifier 50 through their respective coupling conductors 52 and 54. The sync amplifier 50 amplifies the horizontal and vertical sync signals which are then fed to the horizontal and vertical sweep generators 56 and 58 through electrical conductors 60 and 62, respectively. The horizontal sweep generator 56 is coupled to the horizontal deflection electrodes 20 through the conductors 22 which are housed within the cable 24. The vertical sweep generator 58 is coupled to the vertical deflection electrodes 44 through the conductors 46 which are housed within the cable 47.

The video signals carrying the information to be displayed by the instant tube are fed from the receiver 48 to a video amplifier 64 through suitable electrical conductors 66, 68 and 70 for conducting the red, blue and green color control signals, respectively. The video amplifier 64 amplifies these signals and they are then fed through conductors 72, 74 and 76, respectively, to a color gating circuit diagrammatically shown and generally indicated by reference numeral 78. The gating circuit 78 is operative to selectively feed the signals carrying the appropriate color information to the electron gun or guns 12 through an electrical conductor 80.

In the operation of the instant invention, the electron gun of guns 12, upon suitable energization by an incoming video signal (television use), causes electron beams 14, 16 and 18 to be delivered along a path which is in substantial parallel alignment with the longitudinal axis of the linear array of horizontal deflection electrodes 20. Initially, all the horizontal deflection electrodes 20 are maintained at approximately the same potential as the slotted electrode 26. As the electron beams enter the region defined by electrostatic field established by the horizontal deflection electrodes 20, and the slotted electrode 26, the beams may travel unaffected through the field-free region established therebetween until they see a relatively negative field established by the deflection electrode farthest from the gun 12. This field will cause the beams to be deflected downwardly.

In obtaining display, the horizontal deflection electrodes 20 are, as mentioned above, initially maintained at their maximum value and then selectively driven in a negative direction toward a zero potential value. This situation may be described in other words, that is, that initially all the horizontal deflection electrodes 20 are in their fully charged state and then are discharged or driven toward a zero potential value. Whichever method of description is used, the frequency of change is controlled by the horizontal sweep generator 56.

It has been found that satisfactory results were obtained by initially impressing a potential of 800 ivolts positive with respect to the cathode potential of the electron gun 12, while the slotted electrode 26 is also maintained at 800 volts potential positive with respect to the cathode potential of the electron gun 12.

In achieving a line scan, energizing signals are applied to the horizontal deflection electrodes 20 preferably in a successive overlapping manner, such that prior to the instant the potential value on the electrode farthest removed from the gun 12 reaches a sufficiently low potential, a negative going signal is applied to the next adjacent deflection electrode 20. This procedure is repeated along the entire array of electrodes 20 in such a manner that the charge on at least two of the electrodes is always changing at the same time.

The electron beams 14, 16 and 18 after being deflected, accelerated, focused in the primary and transition sections are caused to travel along the path in close proX- imity to the vertical deflection electrodes 44. The vertical deflection system is operated in much the same manne-r in which the horizontal deflection system is operated. The signals applied to the vertical deflection electrodes 44 are preferably applied in overlapping manner so that the potential value on at least two adjacent ones of these electrodes is changing at the same time. Initially, the vertical deflection electrodes 44 lare maintained at a low voltage relative to the composite target screen comprised of the phosphor layers 36, 38 and 40 which are maintained in the order of 16 kv. potential positive with respect to the cathode potential of the electron gun 12. As the beams enter the space between the topmost electrode 44 and the composite target screen, the beams are caused to be deflected toward and into registration with the phosphor material.

As the topmost electrode 44 is driven positive, the so driven electrode allows the beams 14, 16 and 18 to travel downwardly into the region of the next lower electrode 44 which in turn effects deflection of the beams in further continuous registration with composite target screen. It will be readily apparent that when the electron beams are deflected by the horizontal deflection electrodes 20, the beams assume paths which are parallel to one another but are spaced at varying distances from the face of the target screen as clearly shown in Figure 5. Therefore, the deflection forces applied to the beams by the vertical deflection electrodes 44 will cause the beams 14, 16 and 18 to be deflected through different angles with respect to the target screen. The principle upon which this invention is based is that the depth of penetration of electrons is determined primarily by the angle at which the electrons strike the screen while the distance they travel through the screen material is related to their velocity, which in turn varies substantially as the square root of the potential.

It is known that an electron beam will give up rnost of its energy in a particular layer in the material when layers of phosphor are of proper thickness. If, then, three layers 14, 16 and 18 of phosphor material each of which produces a different colored light upon being excited by electron impingement are in superposed relation, a given potential or voltage may be applied to the electron beams to cause them to penetrate the phosphor material a desired depth and to give up most of their energy at that level. Manifestly, such procedure will only excite a single layer of phosphor and will accordingly only produce light of a single color. However, as pointed out hereinabove, the three electron beams 14, 16 and 18 although maintained at substantially the same potential value, may be caused to be deflected through different angles thus causing them to impinge the target screen at different angles. Although, the individual beams `14, 16 and 18 will penetrate and travel in the composite phosphor target screen the same distance, each will come to rest in a different one of the layers 36, 38 or 40 due to the different impingement angles. Thus, due to the angle with which the beam 14 impinges the target screen, it will come to restl and give up its energy in the layer 36 which will give oli red light. The beam 16, being deflected through a greater angle will travel substantially the same distance in the target screen but will come to rest in the layer 38 resulting in the emission of blue light. The beam 18, being deflected through still a greater angle will similar to the beams 14 and 16 travel 75 substantially the same distance through the target screen, but will come to rest and give up its energy in layer 40.

It will be understood that the depth of penetration of the electron beams into the composite target screen may be effected or varied by the relative adjustment of the energy of the electron beams, the thickness of the phosphor layers, the strength of the dellecting force, the spacing of the electron beam from the target, or the type of fluorescent material used.

The target screen may be coated with a film of aluminum to absorb secondary electrons which may be emitted from the phosphor material thereof. Also, it may be desirable in certain applications to employ collection rods A as illustrated in Figures 1 and 2. The rods A are to be operated at a voltage slightly higher than the target screen and may be employed to collect scattered and/or secondary electrons from that part of the target screen struck by the electron beams for the purposes of obtaining a return signal from the screen when such information is deemed desirable.

The double-bend deflection of the electron beam as set forth above prevents beam blow-up and thereby pro vides powerful inherent focusing ability. Specifically, the beam is not brought down to a small spot until the second deflection force is applied to the beams (the force applied by the vertical deflection electrodes 44). As a result of the powerful inherent focusing of this type of deflection system, a large amount of current may be concentrated in the beams resulting in the ability to obtain excellent definition, resolution, and brightness in the displays created on the target screen.

Figure 4 shows another embodiment of the cathode ray tube of the instant invention. In this embodiment, the target screen is formed with phosphor layers 36 and 38 in superposed relationship on one side of the supporting panel 34 while the other side is provided with the phosphor layer 4t). A first source consisting of one or two electron guns is employed; the source being capable of delivering two electron beams 14 and 16 to energize the phosphor layers 36 and 38, respectively. A second source delivers a single beam to energize the phosphor layer 40. The deflection system is substantially identical with that described in connection with Figures 1 and 2.

Figures 6 and 7 show another embodiment of the invention wherein a substantially transparent grid assembly is disposed between the vertical deflection electrodes 44 and the target screen. The grid assembly is comprised of a plurality of small diameter wires 82 and may be operated at a higher voltage than that of the target screen. All of the operating components of the tube are identical with those described in connection with Figures ,l and 2. With the utilization of the grid assembly which is of a higher voltage than that of the target screen, the entrance angle of the individual beams 14, 16 and 18 may be increased considerably as clearly shown in Figure 7.

It will be understood from the foregoing description that according to the `basic concept of the invention all three electron beams may be maintained at a maximum intensity and the angle of impingement with the target screen varied to effect beam travel in the target. In this manner, the beam energy may be maintained practically constant resulting in constant brightness of the image displayed.

In a three electron gun arrangement, the position of each beam with respect to the vertical deflection electrodes may be controlled by suitable energization of the deflection plates associated with the individual guns. Manifestly, such controlling effect will enable the superposed dot registration in the target to be closely regulated by the adjustment of the gun deflection plates in addition to the controlling effect of the relative adjustment of the other factors set forth above. p

There is provided by the present invention a relatively low cost television receiver being capable of producing polychromatic displays. No shadow masks or switching `7 grids are necessary due to the inherent stability of the described type deflection system. The instant tube eliminates the need for vertical and horizontal output transformers or deflection yokes and accordingly, the required power requirements are a fraction of the conventional tubes.

While the present invention has been described with particular reference to a color television system, it must be understood that it has many other applications wherein it is desired to give precise varied color indication in a cathode ray tube. Color radar is one of the more obvious applications of the invention.

According to the provisions of the patent statutes, I have explained the principles and mode of operation of my invention, and have illustrated and described what I now consider to represent its best embodiment. However, I desire to have it understood that, within the scope of the appended claims, the invention may be practiced otherwise than as specifically illustrated and described.

What is claimed is:

1. In a cathode ray tube for use in the presentation of color displays, a phosphor target comprised of a plurality of layers disposed in superposed beam-conducting relation with each other, each layer being capable of emitting a different color as excited by an electron beam, an electron beam source, and means operative to deliver at least one beam into registration with the first target layer at different angles of incidence to correspondingly vary the number of superposed layers penetrated by said beam to thereby selectively excite a correspondingly different one of the phosphor layers.

2. In a cathode ray tube for use in the presentation of color displays, a phosphor target comprised of a plurality of layers disposed in superposed beam-conducting relation, each layer being capable of emitting a different color, an electron beam source, means for delivering at least one beam along an initial path which extends in adjacent nonregistering relation with the target, deflection means for applying a deflecting force to the beam to effect deflection of the beam from said path into registration with said target, and means for adjusting the spacing of the initial beam path relative to said deflection means to different values to thereby vary the angle of incidence of the beam with the target to correspondingly diilerent values to thereby vary the particular phosphor layer excited by the beam.

3. In a cathode ray tube for use in the presentation ofcolor displays, a phosphor target comprised of a plurality of layers disposed in superposed beam-conducting relation, each layer being capable of emitting a different color, an electron beam source including means for delivering a beam along a path in adjacent spaced relation with the target, and deflection means for applying deflecting forces of different values to said beam at a given interval of its path, the value of an applied delecting force being different at successive increments of the distance between the deflecting means and said target, and means for adjusting the spacing of the beam path relative to said target to different values to thereby vary the angle of incidence of registration of the beam with a point on said target, and thereby the particular phosphor layer excited by the beam.

4. In a cathode ray tube for use in the presentation of color displays, a phosphor target comprised of a plurality of layers disposed in superposed beam-conducting relation, each layer being capable of emitting a different color, an electron beam source, means for delivering at least one beam into registration with the rst target layer at different angles of incidence, and means for adjusting the beam in its registration at different angles of incidences to correspondingly different velocities to control same to energize coincident points in the different phosphor layers.

5. In a cathode ray tube for use in the presentation of color displays, a phosphor taget comprised of a plurality of layers disposed in superposed beam-conducting relation, each layer being capable of emitting a different color, means for delivering a plurality of beams along different paths in adjacent nonregistering relation with said target, the paths for the beams for the different colors being at different spaced intervals from the target, and means for applying deflecting forces to the beams at different intervals along their paths to effect deflection of the different beams into registration with correspondingly different intervals on said target, the beam paths being spaced relative to the target and each other to effect excitation of a correspondingly different one of the phosphor layers by the different beams with application of a deflecting force at any interval along the beam paths.

6. In a cathode ray tube for use in the presentation of color displays, a phosphor target comprised of a plurality of layers disposed in superposed beam-conducting relation, each layer being capable of emitting a different color, means for delivering a plurality of beams along different paths in adjacent nonregistering relation with said target, the paths for the beams for the different colors being at different spaced intervals from the target, deflection means disposed adjacent said paths for applying a common deflecting force to said beams simultaneously to deflect same into registration with said target at relatively different angles, and grid means disposed between the first beam paths and the target for further adjusting the angle of the beam registration with said target to provide selective control of the excitation of correspondingly different ones of said layers.

7. In a cathode ray tube for use in the presentation of color displays, a phosphor target comprised of a pluyrality of layers disposed in superposed beam-conducting relation, each layer being capable of emitting a different color, an electron beam source for delivering a plurality of electron beams along a marginal edge of the targets, the paths of the different beams being spaced relative to each other, a primary deflection set disposed along said marginal edge for deflecting said beams into the area adjacent said target in said relative spaced relation, a secondary deflection set for applying dellecting forces to different intervals along its path to effect deflection of the beams into registration with correspondingly diierent intervals on said target, the relative spacing of the beams with the application of a common deflecting force to an interval on the beam paths effecting registration of the different beams with the target at different predetermined angles of incidence to effect excitation of correspondingly different ones of said color layers by the different beams.

8. In a cathode ray tube for use in the presentation of color displays, a phosphor target comprised of a plurality of layers disposed in superposed intimate relation, each layer being capable of emitting a different color, an electron beam source for delivering a plurality of electron beams along a marginal edge of the targets, the paths of the different beams being spaced relative to each other, a primary deflection set disposed along said marginal edge for deflecting said beams into the area adjacent said target in spaced relation with the target and in said spaced relation with each other, a secondary dellection set for applying deflecting forces to different intervals along the beam paths to effect deflection of the beam into registration with correspondingly different intervals on said target, the relative spacing of the beams effecting the application of a deflecting force to an interval on the beam path with registration of the different beams with the target at different angles of incidence and excitation of each of the different layers by a different one of the beams, collector means disposed between said primary and secondary deflection sets, and means for applying energizing potentials to said collector means to maintain same at a higher voltage than the voltage of the screen for secondary emission control purposes.

assunse 9. In a cathode ray tube Ifor use. in the presentation of color displays, a phosphor target comprised of a plurality of layers disposed in s-uperposed beam-conducting relation, each layer being capable of emitting a different color, an electron beam source including means for delivering a beam along different spaced paths adjacent the target, deflection means for applying deflecting forces to an interval along said paths to effect deflection of the beam in the direction of said target, the angle of incidence of the beam with the target being different for the different spaced paths, and beam control means for adjusting the velocity of the beam to different values in its travel along the different paths to thereby vary the particular phosphor layer excited by the beam responsive to application of a given force by said deflection means at a given interval on said beam paths. i

10. In a cathode ray tube for use in the presentation of color displays, a phosphor target comprised of a plurality of layers disposed in superposed beam-conducting relation, each layer being capable of emitting a different color, means for delivering a plurality of beams along different paths spaced at different intervals from said target, means for applying deflecting forces to an interval along said paths to effect deflection of the beams in the direction of said target, the angle of incidence of the different beams with the target thus being of correspondingly different values, and means for adjusting the velocity of the different beams to different values to control the different beams to excite different ones of the phosphor layers responsive to application of said force t said interval.

11. In a cathode ray tube for use in the presentation of color displays, a phosphor target comprised of a plurality of layers disposed in superposed intimate relation, each layer being capable of emitting a different color, an electron beam source for delivering a plurality of electron beams along a marginal edge of the targets, the paths of the different beams being spaced relative to each other, a primary deflection set for selectively defleeting said beams into the area adjacent said target in l said spaced relation, and a secondary deflection set for applying deflecting forces to different intervals along its path to effect deflection of the beams into registration with correspondingly different intervals on said target, the beams being spaced to be controlled with the application of a defiecting force to the beam paths at any given interval to strike the target at different angles of incidence, the path of one beam being at an angle to restrict the travel of the beam to the first layer, the path of a second beam being of a value increased to permit travel of the beam through the first layer and a portion of the second layer, and the path oi the third beam bc-A ing at an angle sucient to effect travel thereof through the first two layersY and at least a portion of the third. 12. In a cathode ray t-ube for use in the presentation of color displays, a phosphor target comprised of a supporting member having a plurality of layers in superposed relation on one surface thereof and at least one layer on a second surface thereof in superposed relation with the layerv on said first surface, each layer being capable of emitting a different color, an electron beam source, means for selectively delivering a beam into registration with said second target surface, and means for delivering at least one beam into registration with said first target surface at different angles of incidence to vary the number of said superposed layers penetrated by said beam to thereby selectively excite a correspondingly different one of the plurality of phosphor layers.

13. In a cathode ray tube for use in the presentation of color displays, av phosphor target including a support member, a plurality of layers disposed in superposed intimate relation with one surface of said support member and at least one layer disposed on a second surface of said support member, each phosphor layer being capable of emitting a different color; an electron beam source including means for delivering a first and second beam along paths adjacent and differently spaced from said one target surfaceand a third beam along a path adjacent a second target surface, means for applying deflecting forces to intervals along said paths to effect deflection of the beams in the direction of the respectively adjacent target surfaces, the angle of incidence of the` first and second b'eams with the target being thus of a correspondingly different value to effect penetration of the respective beams to correspondingly different ones of said first and second layers, and means for adjusting the velocity of the first and second beams to different values to further control the layers excited by the respective beams.

References Cited in the file of this patent UNITED STATES PATENTS 2,455,710 Sze'gho Dec. 7, 1948 2,544,690 Koch et al. Mar. 13, 1951 2,566,713 Zworykin Sept. 4, 1951 2,795,729 Gabor June 11, 1957 2,795,731 Aiken June 11, 1957 OTHER REFERENCES Retailing Daily, Hoffman Flat Color Tube May Hit Market in 2 Years, August 26, 1955.

Gabor: A New Flat Picture Tube, Journal of the Television Society, vol. 8, No. 4, pages 142 to 145.

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