US3178603A

US3178603A - Cathode ray apparatus for character display or conventional cathode ray display

Info

Publication number: US3178603A
Application number: US763215A
Authority: US
Inventors: Moss Hilary
Original assignee: Westinghouse Electric Corp
Current assignee: CBS Corp
Priority date: 1958-09-25
Filing date: 1958-09-25
Publication date: 1965-04-13
Anticipated expiration: 1982-04-13

Description

April 13, 1965 3,178,603

H. MOSS CATHODE RAY APPARATUS FOR CHARACTER DISPLAY OR C ONVENTIONAL CATHODE RAY DISPLAY Filed Sept. 25, 1958 2 SheetsSheet 1 Poi So INVENTOR Hilary Moss AT T'OIQ Apl'll 13, 1965 H. Moss 3,178,603

GATHODE RAY APPARATUS FOR CHARACTER DISPLAY OR CONVENTIONAL CATHODE RAY DISPLAY Filed Sept. 25. 1958 2 Sheets-Sheet 2 Potential Source Fig.8

N 1 LA;

United States Patent 3,178,603 CATHODE RAY APPARATUS FOR CHARACTER DISPLAY OR CONVENTIONAL CATHODE RAY DISPLAY Hilary Moss, Horseheads, N.Y., assignor to Westinghouse Electric Corporation, East Pittsburgh, Pa., a corporation of Pennsylvania Filed Sept. 25, 1958, Ser. No. 763,215 7 Claims. (Cl. 3113- -86) This invention relates to cathode ray apparatus and more specifically to those devices for producing predetermined character shapes on a display screen.

There are several systems in which a cathode ray tube has been utilized to develop character shapes without utilizing scanning techniques applied to the electron beam to cause the beam to scan or write a desired character.

One such device utilizes an electron beam which is scanned over a character shaping member having a plurality of character openings therein such that the electron beam may be selectively positioned over the desired character in the beam shaping member. The beam that emerges from the beam shaping member has a cross sectional configuration corresponding to the shape of the aperture or character of the beam shaping member on which the electron beam is positioned. It is necessary in this type of device that the electron beam after passing through the aperture be returned to the tube axis subsequent to deflection to the desired position on the fluorescent screen. In this type of system, it is necessary in order to select a particular symbol, not only to deflect the electron beam prior to the beam shaping member but also return the electron beam to the tube axis so that the character selection does not cause a shift in the position of the finally displayed character.

Another system utilizes the principle of superimposing an electron beam upon a plurality of character shaped apertures provided in the beam shaping member. The electron beam is of such a cross sectional area as to cover all of the apertures simultaneously. This results in a bundle of differently shaped electron beams emerging from the beam shaping member. A selection system operates on the plurality of electron beams emerging from the beam shaping member. The selection system consists of a deflection system and a disc having a centrally located aperture therein. The deflection system deflects the plurality of electron beams so that only one electron beam will pass through the aperture in the disc member. By proper selection of voltage applied to the deflection system, it is possible to select any one of the character shaped electron beams.

This invention is more particularly directed to this latter type of system, in which a plurality of electron beams representing all of the characters in the beam shaping member is utilized.

It is an object of this invention to provide an improved cathode ray tube for producing a display of selected characters.

It is another object to provide an improved cathode ray tube for producing characters which does not require a system for returning the electron beam to the axis after selecting the desired electron beam.

It is another object to provide an improved cathode ray tube of relatively inexpensive design for providing an improved character shaped beam selection.

It is another object to provide a shorter cathode ray tube providing character shaped beam display.

It is still another object to provide a cathode ray tube to selectively display a normal type scan or a character shaped scan.

These and other objects are effected by my invention as will be apparent from the following description taken 3,l78,603 Patented Apr. 13, 1965 in accordance with the accompanying drawing throughout which like reference characters indicate like parts, and in which:

FIGURE 1 is a View of a cathode ray tube embodying the teaching of my invention;

FIGURE 2 is an elevational view of the cathode surface shown in FIG. 1;

FIG. 3 is an elevational view of the first accelerator selection electrode shown in FIG. 1;

FIG. 4 is a side view of a modified cathode structure which may be embodied in FIG. 1;

FIG. 5 is an elevational view of the cathode structure shown in FIG. 4;

FIG. 6 is a modified selection electrode which may be utilized in FIG. 1

FIG. 7 illustrates another modified beam scanning member which may be utilized in FIG. 1 and used in conjunction with the selection system shown in FIG. 6;

FIG. 8 is a view of a cathode ray tube illustrating another modification of my invention and a system associated therewith;

FIG. 9 is a view of a portion of an electron gun which may be embodied in FIG. 8; and

FIG. 10 illustrates a modified beam shaping member which is incorporated in FIG. 8.

Referring in detail to FIGS. 1, 2 and 3, the basic features of my invention are illustrated incorporated within a cathode ray display tube. The tube may be of any suitable shape and material including a neck portion 10, a flared portion 12 and a viewing window 14. The viewing window 14 is of a suitable light transmissive material such as glass. An electron sensitive coating 16 is deposited on the inner surface of the window 14. The coating 16 may be of a suitable phosphor material that emits light in response to electron bombardment. Positioned within the neck portion 10 of the tube is an electron gun structure 20 for generating and forming an electron beam. A suitable deflection system 18 is also provided for scanning the electron beam over the coating 16 in response to suitable voltages. The deflection system 18 is illustrated as electrostatic but, of course, any other suitable deflection system may be utilized such as electromagnetic.

The electron gun 20 is illustrated schematically and the electron beam generated therein may take many forms and shapes and still fall within the teachings of my invention. The electron gun 20 consists of a cathode 22, a modulator electrode 26, a first accelerator electrode 30, a focusing anode 34 and a final anode 38. The difference in this electrode system over the conventional type electron gun resides in the triode region of the gun consisting of the

electrodes

22, 26 and 30. The cathode 22 consists of a tubular portion 19 closed at the end facing the screen 16 by a member 24. A heater element 21 is 0 provided within the tubular member 19 for providing the necessary heating. The member 24 is transverse to the axis of the neck portion 10. An electron emissive coating 25 is provided on the outer surface of the member 24. The coating 25 is illustrated in FIG. 2 and consists of a plurality of characters formed thereon of electron emissive material such as barium strontium carbonate. The cathode 22 may be operated at a potential near ground with the heater 21 connected to a suitable source for providing the necessary heat to cause the electron emissive coating 25 to emit electrons.

Positioned adjacent to the electron emissive surface 25 is the modulator or control grid 26 which is in the form of a disc or plate perpendicular to the axis of the neck portion 10 and substantially parallel to the member 24. The control grid 26 has an aperture 27 centrally located within the disc. Positioned adjacent to the modulator grid 26 and on the opposite side thereof with respect to the cathode 22 is the first accelerator electrode or selection electrode 39. The selection electrode is comprised of two

segments

31 and 32 of electrically conductive material and electrically insulated from each other and forming an annularly shaped disc with a centrally located aperture 33 therein. The structure of the electrode 30 which is illustrated in FIG. 3 provides two equally

shaped segments

31 and 32 which may be utilized to deflect the electron beam in a vertical direction. The aperture 33 is aligned with the axis of the tube and with the aperture 27. The focusing anode 34 is a tubular member positioned adjacent the electrode 30. Positioned adjacent to the focusing anode 34 is the final anode member 38 which consists of an annular disc shaped member having a centrally located aperture 39. The disc also has a flange about its periphery extending in a direction toward the focusing anode 34. The aperture 39 is also aligned with the aperture 27.

The electrode system consisting of the cathode 22, the modulator electrode 26 and the selection electrode 36 suitably spaced and with the proper voltages applied will project an image of the cathode 22 at the plane of the final anode 33. The spacing and voltages of the system are so chosen that each of the four symbols or characters in the electron emissive coating 25 will fill the aperture 39 in the anode 38. The desired symbol may be made to pass through the opening 39 by applying a difference in potential between the

segments

31 and 32 of the deflection electrode 30. The mean potential of these two

segments

31 and 32 is maintained at the normal first accelerator voltage of about one thousand volts positive with respect to the potential applied to the cathode 24. The potential difference between the two

segments

31 and 32 supplied from a source 37 is varied so that the cone of rays from the triode structure may be deflected to bring any of the four symbols across the aperture 39 in the anode 38. If the voltage of the focusing anode 34 is diminished below the normal focusing potential, the result is an appearance of a fairly sharp cathode image which is the object on the screen. Thus, by proper selection of the voltage applied to the focusing anode 34, the cathode image corresponding in shape to any one of the symbols of the electron emissive coating 25 may be indi cated on the screen 16. When the electron beam is focused, that is when the crossover is the object and is focused on the screen and not the cathode, the spot on the display screen 16 has a structure which is gaussian and which in turn is not dependent on the shape of the emitting cathode area. Thus, a true circular spot is formed when the tube is properly focused and this spot serves to scan a raster on the target 16 in the normal manner. By means of periodically injecting gate signals to the electrode 34, it is thus possible to ring the spot with any of the patterns or characters on the electron emissive coating 25. The character obtained will depend on the voltage applied across the two

segments

31 and 32 of the selection electrode 30. Thus, in the structure described one is able to produce a sharpe pin point spot in the normal scanning operation as well as producing an identifying symbol when desired.

The aperture 27 in the modulator electrode 26 in most cases would have a diameter of from 2 to 3 millimeters. Thus, it can be seen that to attempt to deposit electron emissive symbols of such small area on the cathode is an extremely difiicult operation. The structure illustrated in FIGS. 4 and 5 overcomes this objection. The cathode structure 40 shown in FIGS. 4 and 5 consists of an electrical conductive member 41 which compares to the member 24 in FIG. 1 and on which is deposited a continuous electron emissive coating 42. A beam forming or shaping member 44 is provided of a thin disc of nickel or stainless steel in which the four symbols to be displayed have been etched-out in a manner shown in FIG. 5 and vertically oriented. The disc 44 is mounted slightly away from the electron emissive surface 42 by means of a spacer ring 43 of insulating material. The characters or symbols in the disc 44 may be produced in any suitable manner such as by photographic techniques which allow extreme precision on such small scale items. The gap between the electron emissive coating 42 and the beam forming member 44 is substantially critical and should be about a few thousandths of an inch. The result is that when the cathode is heated, barium from the oxide coating 42 is distilled onto the edges of the various beam forming apertures in the disc 44 and thus the edges of the beam forming apertures become the primary emitting sources. It has been found that this system although not fully understood allows only the edges of the apertures to emit electrons to any extent. Thus, contrary to expectation, the circle aperture, for example, does not emit over the entire area of the aperture but only about its periphery. This is, of course, necessary in order to obtain a circular character on the display screen.

Referring to FIG. 7, a beam forming apertured member 46 is illustrated to show that the structure is not limited to the use of a single line type orientation of symbols. This, of course, allows one to provide a larger number of characters in the beam forming plate. The beam forming plate 4-6 illustrated in FIG. 7 has a plurality of numerals from i to 9 illustrated. In order to provide a two coordinate selection system so that each symbol can be brought over the mask aperture in the electrode 38, the first accelerator or selection electrode must be doubly split as illustrated in FIG. 6. The selection electrode 48 illustrated in FIG. 6 consists of four identically shaped segments 49, 5t), 51 and 52 insulated from each other and having an aperture 53 therein. Suitable deflection voltages are applied to the four segments of the electrode 48 also so arranged that the mean potential is constant thereby allowing one to select the desired symbol on the member 46.

It has also been noted that it may be desirable, as illustrated in FIG. 1, to improve the focusing action of the lens system consisting of the

electrodes

22, 26 and 30 and to equalize the gradients on the cathode surface to make the cathode surface curved. This will produce a flatter image field. The cathode surface is curved such as to be concave with respect to the display screen.

Referring in detail to FIGS. 8 and 9, there is shown a modified structure incorporating my invention. The tube structure is similar to that described with respect to FIG. 1 and only the electron gun and associated deflection system is illustrated in FIG. 8. The electron gun 60 consists of an indirectly heated cathode 64 having an electron emissive coating 66 with a heater element 62 provided for heating the electron emissive coating 66. The cathode 64 is shown connected to ground potential. Positioned adjacent to the electron emissive coating 66 is a beam modulator disc 68 having a centrally located aperture 70. This modulator 68 normally operates at or near cathode potential. Its potential is controlled by a source 67. Positioned adjacent to the modulator or beam focusing electrode 68 is an accelerator anode 72 to which a potential of about 200 volts positive with respect to the cathode 64 is supplied from a suitable source 69.

The anode 72 consists of a tubular portion 74 having its axis coincident with the electron gun axis. A diaphragm 76 is positioned within the tubular portion 74 transverse to the electron beam axis at the end of the tubular member 74 adjacent the beam focusing electrode 68. The diaphragm 76 has an aperture 78 centrally located therein and aligned with the aperture in the beam focusing electrode 68. A second diaphragm 80 is also provided within the tubular member 74 and spaced from the first diaphragm 76. The diaphragm 80 also has an aperture 82 provided therein and aligned with the apertures '78 and 70. This structure provides a small triode and serves merely to produce a cone shaped beam of electrons with a half angle of about 20. After passing through the aperture 82 in the electrode 72, the electrons travel in a field free region for about 1 to 2 centimeters and are then retarded on approaching a beam forming plate 121 such as is illustrated in FIG. 10. The beam forming plate 121 is operated at a potential of up to about volts positive with respect to the cathode 64 by means of a source 71. The beam forming plate 121 as can be seen in FIG. 10, contains the desired characters etched through the surface. The electron beam is of sufficient cross sectional area to illuminate the apertures in the beam forming plate 121. The beam forming plate 121 forms in effect the cathode of the main portion of the cathode ray tube.

This virtual cathode forming structure, including the cathode 64, electrode 68, electrode 72 and beam forming plate 121 is positioned within a cup-shaped member having aperture 92 provided in the bottom portion of the cup-shaped member. The sides of the cup-shaped member 90 are directed away from the screen of the tube and the virtual cathode structure is positioned therein with the beam forming plate 121 adjacent the aperture 92. The electrode serves as the control grid of the main gun. Positioned adjacent to the control grid 90 is a beam deflection electrode 48 similar to that shown in FIG. 6. The control grid 90 operates at a small negative potential with respect to ground supplied from a suitable voltage source 73. An anode 96 is provided adjacent to the deflection electrode 48 and consists of a tubular member 98 coaxial with the axis of the electron beam and having a diaphragm 100 at the end of the tubular member 98 remote with respect to the deflection electrode 48. The diaphragm 100 also has an aperture 102 centrally located therein. It can be seen that the plurality of electron beams generated by the beam forming plate 121 which is a virtual cathode is then focused by the triode system of the virtual cathode containing the desired symbols onto the display screen. The anode 96 containing the aperture 102 is chosen in size so that only the electron rays from one symbol of the beam forming plate 121 can pass through. A selection of the proper symbol is made by varying the potential on the four segments of the segmented deflection electrode 48. It is found that this selection or deflection electrode 48 does not cause a change in the position at which the symbol is projected on the screen. Selection of this position is determined Wholly by the electrostatic or magnetic deflection system illustrated by the deflection system 18 which provide both the vertical and horizontal deflection.

It has been found that the electrode system consisting of the virtual cathode (formed by the beam forming plate 121), the modulator 90 and the deflection electrode 48 provides a desirable lens system. The immersion lens projects an inverted cathode image. The focal length of the immersion lens forming the image depends mainly on the cathode to modulator grid spacing and, for a given potential applied to the first accelerator, on the value of the negative grid bias applied to the modulator grid. When the deflection electrode 48 is split into two or four segments and a voltage difference is applied between them, it is found that the full cone of rays from the triode is bodily deflected about the fixed apex. It is also found that this deflection is accompanied by only negligible distortion of the cathode images. It has been found that it is not essential to apply balanced voltages to the segments of the electrode 48. The acceleration voltage applied to the anode 96 is in no way critical. This voltage, wlnch is supplied from a suitable source 75, is determined almost wholly by the required image brilliance. It has been found that a voltage of about ten kilovolts is satisfactory. In order to utilize the higher voltages on the anode 96, it is, of course, necessary to provide a higher voltage on the electrode 48. It therefore may be necessary to have selecting voltages applied to the electrode 43 of greater than 1,000 volts.

The structure illustrated in FIG. 8 has been modified in FIG. 9 to incorporate an amplifying section for each of the segments of the deflection electrode. In the device shown in FIG. 9, a two segmented electrode 30 is illustrated to simplify the drawing. An amplifier is provided for each

segment

31 and 32. In the specific embodiment shown, an emissive coating is shown on the back surface of the cathode support 122 while an electron emissive coating 66 is provided on the front surface. A common heater, not shown, is provided for both electron emissive coatings 6d and 120. The electron emissive coating 120 is common to the two anodes 124 and 12b. The anode 124 is connected to the segment 31 of the first accelerator 30 and the other anode 126 is connected to the other segment 32 of the electrode 30. It is necessary to also provide a voltage source, not shown, for providing the necessary potential to the two

anodes

124 and 126. A control grid 123 to which the selection signals are applied is associated with the anode 124. A control grid 13% to which selection voltages are applied is associated with the anode 126 for controlling the other segment 32 of the electrode 33. The amplification of each of these triodes may easily be made to have a value greater than 50. A more thorough description of these amplifier structures which are enclosed within the cathode ray tubes is given in U.S. Patent 3,065,368, issued November 20, 1962, entitled Electron Device by E. Atti, and assigned to the same assignee.

In the structure shown in FIG. 8, it is found that for a planar type cathode, the cathode image formed on the screen is itself not in a plane. However, it is nearly so, if the diameter of the cathode being imaged is no more than about of the diameter of the aperture in the control grid. It is found that in such a structure as described that the beam forming plate 121 can be made slightly concave with respect to the fluorescent screen which will result in throwing almost a perfectly fiat image up to an object distance from the axis equal to about A2 of the grid hole radius.

Referring in detail now to the circuit system illustrated in FIG. 8, it has been previously stated that one of the existing weaknesses of present character producing tubes is the fact that they are unable to form the high intensity electron beam spot of the normal cathode ray tube. For several types of applications, it is desirable that such a spot be available. FIG. 8 provides a tube which may produce the usual type picture under normal operation and which on receipt of a command pulse changes to a device presenting characters. In this operation, the tube will put down marking symbols which fall on or near the echo signals and thus can identify them. In this application, it is usually necessary that the distance between the cathode 64 and the beam forming plate 121 be increased over the conventional operation. Furthermore, it is necessary that the beam forming plate 121 be made of a very open mesh construction as is indicated in FIG. 10. The purpose of the open mesh construction is to permit as free a passage as possible to an electron beam. In the case of the embodiment shown in FIG. 10, about 50 percent transmis sion is possible.

To convert the tube from a character producing tube to a normal cathode ray tube, it is necessary to provide a switch which is connected to the beam forming plate 121. The switch 140 provides means of joining the virtual cathode plate either to the accelerator anode 72 or to the small positive potential source 71 of up to about 20 volts. When the beam forming plate 121 is connected to the electrode 72, the tube is intended to operate as a normal cathode ray tube imaging the crossover formed by the triode comprising the

electrodes

64, 68 and 72. The beam intensity may now be controlled in the usual manner by variation of the negative potential on control modulator 68. When the virtual cathode plate 121 is connected to the source 71, the triode composed of the electrodes 64,

63 and 72 ilhiminates the virtual cathode 121 which is imaged by the main

gun comprising electrode

90, 48 and 96. The optics of the gun are so arranged that no change in the potential of the control grid 99 is needed to focus the beam. This, of course, simplifies the switching operation. This is accomplished in this electrode configuration on account of the freedom with which the positive potential of the electrode 72 may be selected. It has been found that variations in the potential of the source 69 have very little eflect on the virtual cathode imaging conditions. It is thus possible to choose the amount of voltage from the source 69 after the tube is set up so that the cross-over formed by the triode structures 64, 63 and 2 2 is focused without change in the potential on the control grid from source 73. The brightness of the spot when the device is operated as a normal cathode ray tube is controlled by the potential source 67 applied to the modulator 68. The switch 140 is illustrated as only mechanical but it is of course obvious that it may comprise a thermionic trigger of some sort requiring only a single pulse to effect the switching operation. When in the normal cathode ray tube operation position, ail elements of the selector electrode 48 would normally be at the same potential as the final anode In order to avoid confusion between an echo and its identifying symbol, it might be desirable that this be effected by slightly tilting the

portions

64, 68 and 72 of the gun. This will not change the position of the beam forming plate 121.

In practice, higher character brightness on the fluorescent display screen would normaily be achieved by the use of post deflection acceleration of the shaped electron beam.

While I have shown my invention in only a few forms it will be obvious to those skilled in the art that it is not as limited but is susceptible of various other changes and limitations without departing from the spirit and scope thereof.

I claim as my invention:

1. A cathode ray display system comprising an electron sensitive target, a beam generating means for supplying and directing a primary beam of electrons along a given path, said beam generating means comprising a cathode, a control grid having an aperture therein and an accelerating electrode, a beam shaping member positioned transverse to the path of said electrons leaving said accelerating electrode, said beam shaping member comprising a plurality of areas, each of said areas having a character shaped aperture provided therein, said areas of said beam shaping electrode positioned to minimize the amount of electron beam interception, said character shaped apertures providing a plurality of character shaped electron beams, a first electrode member having a diaphragm and an aperture provided therein and positioned adjacent to said beam shaping member for focusing the character shaped electron beams from said beam shaping electrode to a composite beam crossover, a first deflection means including a plurality of electrically insulating members encompassing said character shaped electron beams and positioned near said crossover, a second electrode including a diaphragm and having an aperture provided therein positioned between said first deflection means and said electron sensitive target, the aperture in said diaphragm of said second electrode being adapted to pass a predetermined character shaped electron beam, said first deflection means provided for directing one of the plurality of character shaped electron beams through the aperture in said diaphragm of said second electrode, a second deflection means positioned between said second electrode and said screen [or deflecting the character shaped electron beam emerging from said diaphragm of said second electrode onto said target in which the object is the beam shaping member and means associated with said electron gun for secondly focusing the composite beam on said electron sensitive target whereby substantially all of emerging electrons from said beam shaping member are formed into a spot of high electron density on said electron sensitive target and in which the object is the composite beam crossover.

2. A cathode ray tube display system comprising a target member, an electrode structure for generating an electron beam for scanning said target member, said electrode structure comprising a beam shaping member having a plurality of character shaped apertures therein, a first electrode system positioned on the opposite side of said beam shaping member with respect to said target comprising a cathode, a control grid and an accelerating electrode for generating an electron beam to form a first cross-over near said control grid and superimposing said electron beam over the character shaped apertures in said beam shaping member, a second electrode system positioned on the opposite side of said beam shaping member with respect to said first electrode system, means for establishing a retarding electric field near said beam shaping member to reduce the velocity of the electrons within the electron beam generated by said first electrode system within the immediate region of said beam shaping member to form in effect a virtual cathode for said second electrode system, said second electrode system comprising a control grid and a selection electrode operating at a voltage to form a second crossover near said selection electrode, said selection electrode including a plurality of insulating members encompassing the character shaped electron beams emerging from said beam shaping member, a first electrode member including a diaphragm and having an aperture provided therein positioned between said selection electrode and said target and means for applying a diiference in potential to said insulated members of said selection electrode to deflect said character shaped electron beams emerging from said beam shaping member about a common apex located at said crossover to selectively allow one of said character shaped beams to pass through the aperture in said diaphragm of said first electrode member to said target in which the object is the beam shaping member.

3. A cathode ray display system comprising a target member, an electrode structure for generating an electron beam for scanning said target, said electrode structure comprising a beam shaping member having a plurality of character shaped apertures therein, a first electrode system positioned on the opposite side of said beam shaping member with respect to said target comprising a cathode, a control grid and an accelerating electrode for generating a primary electron beam. to form a first crossover near said control grid and superimposing said primary electron beam over the character shaped apertures within said beam shaping member, a second electrode system positioned on the opposite side of said beam shaping member with respect to said first electrode system, means for establishing a retarding electric field near said beam shaping member to reduce the velocity of the electrons emerging from the character shaped apertures in said beam shaping member to form in effect a virtual cathode for said second electrode system, said second electrode system comprising a control grid and a selection electrode operating at a voltage to form a second crossover near said selection electrode, the control grid of said second electrode system comprising a diaphragm having an aperture therein through which the eiectron beams from said beam shaping member pass, said selection electrode of said second electrode system including a plurality of insulated members positioned about the character shaped electron beams, an anode member including a diaphragm and provided with an aperture therein positioned between said selection electrode and said target and means for applying a diiierence in potential to said insulated members of said selection electrode to deflect said character shaped electron beams about a common apex located at said second crossover and to selectively allow one of said beams to pass through the aperture in said anode to said target.

4. A cathode ray tube system comprising a target memher, an electrode structure for generating an electron beam for scanning said target member, said electrode structure comprising a beam shaping member having a plurality of character shaped apertures therein, a first electrode system positioned on the opposite side of said beam shaping member with respect to said target comprising a cathode, said first electrode system including a control grid and an accelerating electrode for generating an electron beam to form a first crossover near said control grid and superimposing said electron beam over the character shaped apertures within said beam shaping member, a second electrode system positioned on the opposite side of said beam shaping member with respect to said first electrode system, means for establishing a first potential on said beam shaping member to reduce the velocity of the electrons Within the immediate region of said beam shaping member to form in eifect a virtual cathode for said second electrode system, said second electrode system comprised of a control grid and a selection electrode operating at a voltage to form a second crossover near said selection electrode, said selection electrode including a plurality of insulated members encompassing the character shaped electron beams emerging from said beam shaping member, an anode comprising a diaphragm having an aperture therein, said anode located between said selection electrode and said target, means for applying a difference in potential to said insulated members of said selection electrode to deflect said electron beams emerging from said beam shaping member to selectively allow one of said beams to pass through the aperture in said anode and onto said target to form a character shaped spot in which the object is the beam shaping member and means for establishing a second potential on said beam shaping member and equal voltages on the insulated members of said selection electrode to focus said electron beam onto said target to form a spot of high electron density in which the object is the first crossover.

5. In a cathode ray tube system comprising a target, a first electrode system for generating an electron beam and forming a first crossover of said beam, a beam shaping electrode positioned Within the path of said beam having a plurality of character shaped apertures therein and onto which said electron beam is directed to produce a plurality of character shaped electron beams from the opposite side thereof, a second electrode system positioned on the opposite side of said beam shaping member with respect to said first electrode system comprising a control grid having an aperture therein, a selection electrode comprising a plurality of insulated members encompassing the character shaped electron beams emerging from said beam shaping member and an anode member including a diaphragm having an aperture therein provided between said selection means and said target, the combination comprising means for applying a first potential to said beam shaping member to focus the electron beam onto said target to obtain a small area spot of high electron density in which the object is the electron beam at the first crossover and means for applying a second potential to said beam shaping member and of a more negative potential than said first potential so that the velocity of the electrons emerging from said beam shaping member is of a low value such that said beam shaping electrode acts as a virtual cathode for said second electrode system and said second electrode system forms a second'crossover near said selection electrode and means for applying a voltage differential between said insulated members of said selection electrode to selectively allow one of said character shaped electron beams to pass through the aperture in said anode and form a character shaped spot on said target in which the object is the electron beam shaping electrode.

6. A shaped beam tube comprising means for emitting electrons to form an electron beam, a matrix electrode having a plurality of character shaped apertures positioned in close proximity to said electron emitting means,

said matrix being at a low potential with respect to said electron emitting means, means for causing electrons emitted from said electron emitting means to traverse the character shaped apertures in said matrix and emerger as a plurality of distinguishable character shaped electron beams, a target member for receiving the electrons emitted from said electron emitting means, an electrode focusing means positioned between said matrix and said target for firstly selectively passing one of said character shaped electron beams to said target member in which the object is said matrix and then secondly for focusing a substantial part of the electron beam onto said target member in a spot of high electron density in which the object is the first crossover of said beam.

7. A cathode ray display system comprising an electron sensitive target, an electron gun structure comprising a beam generating means for supplying and directing a primary beam of electrons along a given path, a beam shaping member positioned across the path of said primary beam of electrons, said beam shaping member operating at a potential such that the electrons in said primary beam of electrons are reduced in velocity on arriving in the immediate region of said beam shaping member, said beam shaping member having character shaped openings for providing a plurality of character shaped electron beams emerging from said openings on interception of said primary beam, a first electrode member positioned adjacent to said beam shaping member on the side of said beam shaping member facing said electron sensitive target for forming and directing the character shaped electron beams to a composite beam crossover, a first deflection means including a plurality of electrically insulated members surrounding said character shaped electron beams and positioned near said crossover, a second electrode including a diaphragm having an aperture therein positioned between said first deflection electrode means and said electron sensitive target, the aperture in said diaphragm being adapted to pass one of said character shaped electron beams, a first circuit means operatively associated with said electron gun structure to direct and focus one of said character shaped electron beams through said aperture in said diaphragm and onto said electron sensitive target in the form of said shaped character in which the object is the beam shaping member and a second circuit means operatively associated with said electron gun to direct and focus the composite beam crossover onto said electron sensitive target whereby substantially all of the emerging electrons from said beam shaping member impinge on said electron sensitive target to provide a spot of high electron density in which the object is said composite crossover and switching means for selectively applying said first or second circuit means to said electron gun.

References Qited by the Examiner UNITED STATES PATENTS 2,283,383 5/42 McNaney 315-1 2,761,988 9/56 McNaney 313-86 XR 2,790,103 4/57 McNaney 3 151 2,811,668 10/57 McNaney 3151 2,844,759 7/58 Bryan 313-70 2,862,144 11/58 McNaney 315-1 2,870,361 1/59 Aiken 315l FOREIGN PATENTS 521,803 5 40 Great Britain.

OTHER REFERENCES Anthony: New Apparatus and Techniques of Air Traffic Control Data Handling and Display, I.R.E. Convention Record, vol. 3, part 10, 1955.

ROBERT SEGAL, Acting Primary Examiner.

RALPH G. NILSON, ARTHUR GAUSS, Examiners.

Claims

6. A SHAPED BEAM TUBE COMPRISING MEANS FOR EMITTING ELECTRONS TO FORM AN ELECTRON BEAM, A MATRIX ELECTRODE HAVING A PLURALITY OF CHARACTER SHAPED APERTURES POSITIONED IN CLOSE PROXIMITY OF SAID ELECTRON EMITTING MEANS, SAID MATRIX BEING AT A LOW POTENTIAL WITH RESPECT TO SAID ELECTRON EMITTING MEANS, MEANS FOR CAUSING ELECTRONS EMITTED FROM SAID ELECTRON EMITTING MEANS TO TRAVERSE THE CHARACTER SHAPED APERTURES IN SAID MATRIX AND EMERGER AS A PLURALITY OF DISTINGUISHABLE CHARACTER SHAPED ELECTRON BEAMS, A TARGET MEMBER FOR RECEIVING THE ELECTRON EMITTED FROM SAID ELECTRON EMITTING MEANS, AN ELECTRODE FOCUSING MEANS POSITIONED BETWEEN SAID MATRIX AND SAID TARGET FOR FIRSTLY SELECTIVELY PASSIN GONE OF SAID CHARACTER SHAPED ELECTRON BEAMS TO SAID TARGET MEMBER IN WHICH THE OBJECT IS SAID MATRIX AND THEN SECONDLY FOR FOCUSING A SUBSTANTIAL PART OF THE ELECTRON BEAM ONTO SAID TARGET MEMBER IN A SPOT OF HIGH ELECTRON DENSITY IN WHICH THE OBJECT IS THE FIRST CROSSOVER OF SAID BEAM.