US3205391A

US3205391A - Negative-lens type deflection magnifying means for electron beam in cathode ray tubes

Info

Publication number: US3205391A
Application number: US697240A
Authority: US
Inventors: Nicholas D Glyptis
Original assignee: MULTI TRON LAB Inc
Current assignee: MULTI TRON LAB Inc; MULTI-TRON LABORATORY Inc
Priority date: 1957-11-18
Filing date: 1957-11-18
Publication date: 1965-09-07
Anticipated expiration: 1982-09-07

Description

Sept. 7, 1965 3,205,391

PE DEFLECTION MAGNIFYING MEA N. D. GLYPTIS NEGATIVE-LENS TY NS FOR ELECTRON BEAM IN CATHODE RAY TUBES Filed Nov. 18, 1957 5 Sheets-Sheet 1 N. D. GLYPTIS 3,205,391 NEGATIVE-LENS TYPE DEFLECTION MAGNIFYING MEANS FOR ELECTRON BEAM IN CATHODE RAY TUBES Filed NOV. 18, 1957 5 sneets sheet 2 pmmm%w QflaQM $9,972

53 d WM Sept. 7, 1965 N. D. GLYPTIS 3,205,391

' NEGATIVE-LENS TYPE DEFLECTION MAGNIFYING MEANS FOR ELECTRON BEAM IN GATHODE RAY TUBES Filed Nov. 18, 1957 5 Sheets-Sheet 3 Se t. 7, 1965 N. D. GLYPTIS 3,205,391

NEGATIVE-LENS TYPE DEFLECTION MAGNIFYING MEANS FOR ELECTRON BEAM IN CATHODE RAY TUBES 5 Sheets-Sheet 4 Filed NOV. 18, 1957 Sept. 7, 1965 N. D. GLYPTIS I NEGATIVE-LENS 3,205,391 TYPE DEFLECTION MAGNIFYING MEANS FOR ELECTRON BEAM IN CATHODE RAY TUBES Filed Nov. 18, 1957 5 Sheets-Sheet 5 INVENTOR. %0 s BY v w/v/zeyg United States Patent NEGATIVE-LENS TYPE DEFLECTIGN MAGNIFY- ING MEANS FOR ELECTRON BEAM IN CATH- ODE RAY TUBES Nicholas D. Glyptis, Westchester, Ill. Multi-Tron Laboratory, Inc., 4624 W. Washington, Chicago, Ill.)

Filed Nov. 18, 1957, Ser. No. 697,240 32 Claims. (Cl. 313-46) This invention relates to a beam deflection device and more particularly to an improved beam deflection device in which the beam is projected toward a target followmg deflection.

In beam deflection devices, for example cathode-ray tubes, a beam is formed, shaped and deflected by suitable elements and is accelerated directly from the area of the deflection toward a target by a field which applies an accelerating force to the beam. One object of the invention is to provide a novel beam deflection device in which the image formed by a deflected beam is projected toward a target. The power required to effect a given angular deflection of the beam is dependent to a large extent upon the velocity of the beam during deflection; and this has placed an upper limit on the angle of deflection which may be achieved with conventional deflection which may be achieved with conventional deflection circuitry and components. By projecting the deflected image in an enlarged configuration on the target, deflection may be accomplished at a low energy level. Another object is that the image may be projected either by retracting or by reflecting the beam toward the target.

Still another object is to provide a beam deflection device including a beam source, a target, means for deflecting the beam, means establishing a field condition for accelerating the beam toward the target, and means for modifying the field condition adjacent the deflecting means, with the angle of incidence of the beam on the lines of force of the field being at least 90 throughout substantially the entire deflection range. A further object is to provide such a device in which the means interposed between the deflecting means and target establishes a field boundary condition adjacent the deflecting means.

Another object is that the field boundary condition is established by means of a grid interposed between the deflecting means and target and adjacent the deflecting means. Yet a further object is to provide a grid having alternate solid portions and openings in which the crosssectional diameter of the beam at the grid is greater than the area of an opening.

Another object is to provide a beam deflection device including a beam source, a target for the beam, means for accelerating the beam along the first path, means associated with the first path for deflecting the beam, means for reflecting the deflected beam along a second path, and means for accelerating the beam along the second path toward said target. Yet a further object is to provide such a device in which the first path is generally parallel to the target and the second path is generally at right angles thereto. And another object is that the reflecting means includes a grid structure and a reflector plate mounted to intercept the beam in said first path.

Another object is to provide a beam deflection device including an envelope, cathode, beam intensity control and beam shaping elements all carried by supporting means in the envelope, means for establishing a beam deflection field carried by the supporting means, means for establishing a field for accelerating the beam toward the target, and a grid carried by the supporting means and interposed between the deflection means and target and adjacent the deflection means. A further object is to provide a device in which the deflection establishing "Ice means includes a member of insulating material carried by the supporting means and having conductive areas thereon.

Still a further object is to provide a device including a beam source, a target, means for deflecting the beam toward desired positions on the target, means for establishing a field condition for applying an accelerating force to the deflected beam, with the accelerating force acting substantially along the path of the deflected beam, and means for varying the intensity of the field condition for imparting a velocity modulation to the deflected beam. Another object is to provide such a device in which the field of varying intensity is established between parallel surfaces.

These and other specific objects and advantages of the invention will be apparent from the following detailed description and drawings, in which:

FIGURE 1 is a side view, partially in section, of a cathode-ray tube embodying the invention;

FIGURE 2 is an enlarged fragmentary view of a portion of FIGURE 1;

FIGURES 3, 4 and 5 are diagrammatic views illustrating the eflect of different forms of grid surfaces;

FIGURE 6 is a diagrammatic view of a modified form or" the invention;

FIGURE 7 is a view similar to FIGURE 1 of another modified form of the invention;

FIGURE 8 is a view similar to FIGURE 1 of a further modified form of the invention;

FIGURE 9 is a fragmentary sectional view of another modified form of the invention;

FIGURE 10 is a sectional view taken substantially along line 1fl-10 of FIGURE 9;

FIGURE 11 is a sectional view of a beam deflection amplifier embodying the invention;

FIGURE 12 is a sectional view of another embodiment of the invention; and

FIGURE 13 is an enlarged fragmentary view taken generally along line 13-13 of FIGURE 12.

While the invention is susceptible of various modifications and alternative constructions, it is herein shown and will hereinafter be described in certain preferred embodiments. It is not intended, however, that the invention is to be limited thereby to the specific constructions disclosed. On the contrary, it is intended to cover all modifications and alternative constructions falling within the spirit .and scope of the invention as defined in the appended claims.

Although this invention is susceptible of application of many types of beam deflection devices, it is illustrated and will be described herein principally in connection with cathode-ray tubes.

As pointed out briefly above, the deflection energy required for a given angular deflection of a beam is a function of the velocity of the beam as it passes through the deflection region. In turn, the energy of the beam itself is dependent on the velocity. For example, in a cathoderay tube the light output depends, among other parameters upon the velocity with which the electrons of the beam impinge upon the surface of the screen or target. Present commercial cathode-ray tubes represent, among other considerations, a compromise between the desired light output and the limitations of practical deflection. With the present invention the beam may be deflected through a small angle to provide a relatively small image which is then projected on the screen of the tube. As a corollary feature of the invention, deflection is effected while the beam has a relatively low velocity and the velocity of the deflected beam is increased before the beam strikes the target. Projection by refraction will be discussed first.

Turning now to FIGURES l and 2, a cathode-ray tube is shown having an envelope 21 on the interior surface of the face 21a of which is deposited a suitable material, such as a phosphor 22. Mounted in the neck portion 23 of the tube 20 is an electron gun assembly, indicated generally as 24, which includes a source of electrons, as a heated cathode having an emissive surface, a control grid for varying the intensity of the beam of electrons emitted from the cathode and suitable beam shaping elements. The phosphor layer 22, which luminesces when a beam of electrons impinge upon it, serves as a target or screen for the beam.

A' deflection yoke assembly 25 is mounted on the neck 23 of the tube and includes deflection coils which may be energized with suitable deflection currents to scan the electron beam over the screen. Interposed between the deflection region, i.e. the region inside the tube bounded by the deflection coils, and the screen or target 22 is a grid 26 which may be of a wire mesh material.

Suitable operating connections may be made to the elements of the electron gun through prongs 27 at the base of the tube and to the screen 22 by means of the connector 28, extending through the wall of the envelope.

As best seen in FIGURE 2, the grid 26 is connected, by means of a conductive coating 29, as Aquadag, a graphite-water glass emulsion, deposited on the interior surface of the envelope 21 and a conductor 30 with one of the elements of the electron gun 24, as accelerating element 31. Assuming that the cathode of the device is operated at or about ground potential, a positive voltage of the order of 1,000 volts or so may be applied to the accelerating element 31 and thus to grid 26. A higher accelerating voltage, as of the order of 10,000-15,000 volts is applied to the target 22 through the connector 28 and a high voltage conductive coating 32, deposited on the interior of the rear portion of the envelope. The high voltage conductive coating 32 is insulated from the grid 26 and the low voltage coating 2-9 by means of an insulating coating 33, as of chromic oxide. It will be understood that the thickness of the

coatings

29, 32 and 33 on the interior surfaces of the envelope is exaggerated in the drawings.

Inasmuch as the electron beam, when it enters the deflection region, has been accelerated only to the extent of the voltage applied between the cathode and the grid 26, its velocity is relatively low and deflection may be achieved with a correspondingly small amount of power. The major portion of the acceleration of the electrons in the beam occurs between grid 26, a boundry of the accelerating field, and the screen or target 22.

The shape of the grid 26 and its relationship to the deflection region, and to a lesser extent its relationship to the screen of the tube, determine the refractive effect on the deflected beam of electrons passing through the field boundary. Three possibilities will be discussed. In FIGURE 3, the grid 49 defines a surface which is a portion of a sphere and is so located that the center 41 of the spherical grid surface coincides with the center of deflection, or the center of the deflection volume, defined by the deflection coils 42. In this case, the deflected beam 43 maintains its direction as it passes through the grid 40. In FIGURE 4, the generally spherical grid surface is replaced by a straight or planar grid 44. With this construction, the electron beam 45 is bent inwardly toward the center of the screen 46 as it passes through the grid; a positive lens effect. In FIGURE 5, the grid 47 is again a generally spherical surface. However, the center 47a about which the grid surface is formed is spaced away from the center 48 defined by the deflection coils 49, in a direction toward the screen 50 of the tube. In this case, the electron beam 51, as it passes through the grid 47, is bent outwardly away from the center axis of the tube. This may be described as a negative lens effect.

These various conditions may be described in another manner by considering the angle of incidence of the electron beam on the electrostatic field between the accelerating field modifying grid and the screen of the tube. If the beam enters the field in a direction normal or generally at right angles to the field, the beam is not bent or refracted. This is the condition of FIGURE 3 and may be described as a zero lens effect. If the angle of incidence of the beam on the accelerating field is less than the beam will be refracted or bent inwardly toward the center of the tube as shown in FIGURE 4. However, should the angle of incidence be greater than 90, the beam is bent outwardly, FIGURE 5, in a manner which magnifies the effect of the deflection field set up by the deflection coils. These effects are sometimes referred to herein as electron optical projection, or EOP.

It is believed that most applications of the invention will make use of an accelerating field modifying structure which has either a Zero or a negative lens effect. However, it is to be understood that the shapes of the grids may be varied and a positive lens effect may be desirable in some cases, as where it is desired to compensate for an irregularity in the face or screen of the tube, or for some other special purpose. In fact, a grid or grids having two or even all three characteristics might be used in a single device.

Returning now to FIGURE 1, the grid 26 is generally spherical and is formed about the center of deflection defined by deflection coils 25, providing a Zero lens effect. With the structure shown, a standard deflection circuit such as used in television receivers, may be used to effect scanning of a tube. The tube illustrated in this figure is representative of the widest scan tube presently available commercially. The screen itself has a major axis of 20% inches, a minor axis of 16% inches and a diagonal dimension of 21 /3 inches. The depth of the tube from the outside of the face of the screen to the base 27, indicated at 55, is 9 inches, while the distance from the face of the screen to the rear of the deflection coils, indicated at 56, is 6 inches. In order to scan the screen of this tube, without the use of the accelerating field modifying grid 26, it is necessary to use special deflection circuitry, including a water-cooled deflection yoke. With the accelerating field modifying grid 26 the tube may be scanned with standard commercial television receiver circuitry, using for example a 6BQ6 power amplifier in the horizontal sweep circuit and a 12BH7 in the vertical sweep circuit.

FIGURE 7 illustrates how electron optical projection may be utilized to scan an ultrashort cathode-ray tube. The tube of FIGURE 7 has screen dimensions comparable to those of FIGURE 1, however, the envelope 61 of the tube is much more shallow, the tube neck 62 is shorter and the electron gun 63 is reduced in length. The overall dimension of this tube from the face of the screen to the base, indicated at 64, is 3% inches. The accelerating field modifying grid 65 has an ellipsoidal shape designed to provide a negative lens effect. The sweep circuits and deflection coil 66 are designed to provide 150 scanning. However, with the additional coverage provided by the negative lens effect of grid 65, the electron beam 67 scans an angle of on the screen of the tube.

The accelerating field modifying grid is preferably formed of a wire mesh material with relatively fine weave and small wire. For example, woven wire material with a 50 x 50 mesh, of wire 1 mil in diameter has been found satisfactory. The wire is preferably stainless steel with a carbonized surface to reduce secondary emission effects. The grid may be secured in place in any suitable manner, as by porcelain cement.

It is preferable that the cross-sectional area of the electron beam as it passes through the accelerating field modifying grid be substantially greater than the areas of the openings between the grid wires, in order to reduce undesired side effects, such as aberration. With the grid described above, the electron beam covers approximately four openings between the wires of the grid. It should be kept in mind, of course, that when the beam is properly focused, so that it forms a sharp trace on the screen of the tube, its cross-sectional diameter is much greater in the vicinity of the field modifying grid as it is not focused there.

Secondary electrons emitted from the grid are subject to a very strong action from the individual lenses formed by the wires of the grid, scattering them at random through the tube where the majority strike the conductive interior coating and are dissipated. As the grid is spaced from the screen a substantial distance, any secondary electrons which reach the screen arrive in a random fashion and at worst increase the background light level of the picture. They do not form an image on the screen.

FIGURE 8 shows electron optical projection applied to a present day experimental tube designed for 150 deflection. The face of the tube has a minor axis of 21.7 inches and a major axis of 26.3 inches. The overall length of the tube from the face of the screen to the rear of the base is of the order of nine inches. The grid 70 shown in the upper half of the tube is designed for straight-line projection, 01 a zero lens effect, in connection with a deflection system including deflection coil 71, designed for 150 scanning. The grid 72 shown in the lower half of the tube provides a negative lens effect in connection with a scanning system including deflection coil 73, designed for about 170 scanning.

FIGURE 6 shows a modification of the structures described above for use in a system employing velocity modulation of the electron beam. Again, a beam is deflected by suitable currents passing through coils 80 at a low energy level, as the grid 81 is operated at a potential much lower than that of the screen 82. A second grid 83 is interposed between the grid 81 and the screen 82 of the tube. The

grids

81 and 83 are parallel and are generally spherical in configuration, about the center of deflection of coils 80. Connected between the

grids

81 and 83 is an alternating signal source 84 which establishes a constantly varying potential between the grids. This in turn causes bunching of the electrons as they pass between the grids, eifecting velocity modulation of the electron beam. If desired, the velocity accelerating potential may be applied between the grid 83 and the screen 82 of the tube or between the grid 81 and the screen 82, if the grid 83 is eliminated, as shown in broken lines. In order to achieve linear velocity modulation over the entire scan range of the deflection system, it is necessary that the accelerating potential be applied between parallel surfaces so that the path of the electron beam is normal to the lines of force of the varying field.

A combined beam deflection, velocity modulation device can be utilized in magnetrons, klystrons, traveling Wave tubes and the like to achieve an extremely wide frequency range with a single unit. For example, a klystron may have several cavities with a single electron beam source. Deflection means, as plates or coils, act on the beam to deflect it toward a desired cavity. In passing from the deflecting means to the cavity, the beam is velocity modulated as described in connection with FIGURE 6.

The multiple grid structure of FIGURE 6 may also be used with grids having a negative lens eifect to achieve a desired degree of projection of the image scanned by the beam in a series of steps. This is preferable where projection is relied on to expand the size of the image a substantial amount, as the distortion introduced by a series of relatively small refraction steps is less than that resulting from a single refraction yielding the same end result.

FIGURE 9 illustrates another means for reducing the power necessary to effect the desired deflection of the beam. The power required is a function, not only of the velocity of the beam in the deflection region, but also of the volume of the deflection region, i.e. the volume within the deflection coils. Present magnetic deflection systems are limited by requiring that the deflection coilsbe mounted on the outside of the neck of the tube. Thus the deflection volume may not be reduced more than is permitted by the size of the tube neck, and this is also limited by the size of the elements which make up the electron gun. In FIGURE 9, the electron gun has mounted on the end thereof a tubular member 91 of insulating material, as glass. Formed on the surface of the tubular member is a conductive area 92, which in the embodiment shown forms a coil. A similar coil 92a is provided on the other side of the tubular member 91 while a second pair of conductive coils 92b and 920 are formed on the inside of the tubular member (FIGURE 10). Suitable connections (not shown) may be made to the ends of the

coils

92, 92a, 92b and 92c through the neck of the tube and the prongs at the end thereof by means of which the deflection currents may be applied to the coils. The scanning field set up by these currents is thus concentrated in the area in which it is needed, im mediately adjacent the electron beam, and the deflection volume of the system is substantially reduced, resulting in a saving in power.

In the case of an ultrashort tube, such as that shown in FIGURE 9, the electron gun and deflection structur may extend from the neck of the tube 93 into the interior cavity of the envelope. If it is not practical to achieve scanning of the screen 94 of the tube with straight deflection, an accelerating field modifying grid 95 may be mounted on the end of tubular member 91. In this case, the grid 95 preferably has a negative lens eifect configuration. It is preferable that the tubular member 91 have a generally parabolic configuration, following the parabolic deflection path of the electrons as they pass through the deflection field.

A tube combining the features of FIGURES 7 and 9 has no neck at all. The entire electron gun and deflection system is inside the body of the envelope, with only the connector pins extending therefrom.

FIGURE 11 illustrates the application of the principle of electron optical projection to a beam deflection amplifier tube 100. In a beam deflection tube, an electron beam formed from electrons emitted from a cathode 101 is directed by potentials applied to

deflection plates

102 and 103 to one or the other of two anodes 104 and 105. An accelerating field modifying grid 106 is interposed between the

deflection plates

102 and 103 and the anodes 104 and 10S, and a voltage substantially lower than that of the anodes is applied thereto. As discussed above, the power necessary to effect deflection of the electron beam is substantially reduced, permitting the beam deflection amplifier to operate with greater sensitivity.

FIGURE 12 illustrates reflective electron optical projection embodied in a cathode-ray tube 110, which has a target or screen 111 on one face thereof. The neck 112 of the tube, which houses the electron gun structure extends from the edge of the tube envelope, rather than from one of the major sides. Deflection coils 113 are provided about the neck of the tube for scanning the beam, and defining a deflection volume having a center of deflection 113a. Mounted at about the midpoint of the interior of the wall of the tube opposite the screen or target 111 is a reflecting structure 113 including a grid 115 and a reflector plate 116.

A positive accelerating voltage applied to grid 115 causes the electrons from the gun structure in tube neck 112 to accelerate along a first path, generally parallel with the tube screen 111. During traversal of this path, the beam is scanned by currents applied to deflection coils 113 in such a manner that the desired image is formed on grid 115. Reflector plate 116 has applied thereto a positive voltage which is lower than or negative with respect to the voltage applied to grid 115; while a final accelerating voltage, much higher than the voltage applied to grid 115 is applied to the screen 111. Grid 115 is made up of a small number of very fine wires, suflicient to establish the desired accelerating voltage along the first path, without interrupting a substantial portion of the electron beams. Accordingly, as the electron beam accelerates toward the grid 115, the greatest part of it passes through, whereupon it changes direction, as the reflector plate 116 is negative with respect to grid 115, and is accelerated along a second path toward the screen 111. It will be noted that electrons scanned toward the top of grid 115 (as viewed in FIGURE 12) along the path 118 are reflected along a second path 118a, to the top of screen 111. Beams following the path 119 to the center of grid 115 are reflected along a path 11% to the center of screen 111 while electrons deflected along path 120 are reflected from the lower end of grid 115 along path 120a to the lower portion of screen 111 The size and shape of grid 115 and reflector plate 116 are dependent on the shape, size and curvature of the target 111. As shown in the drawings, the grid and reflector plate may be round and slightly concave, in order to achieve the desired reflecting characteristics.

A shield 121, which may be a grid-like structure, is provided between the screen 111 of the tube and the first path of the electrons, between the deflection zone and the reflecting means 114, to prevent the high accelerating voltage applied to the screen from affecting the deflection operation.

In a tube with the cathode operated at about ground potential, reflector plate 116 has a positive voltage of the order of several hundred volts applied thereto. Grid 115 is operated within the range of one-half to two-thirds of the ultor or screen voltage which may be of the order of 15,00020,000 volts. This isolating grid structure 121 is operated at ground, or a low positive potential.

I claim:

1. A beam deflection device, comprising: a beam source; target means for said beam; means for deflecting said beam in two dimensions to desired positions on said target means; means establishing a field condition for accelerating said beam toward said target means; and means modifying said field condition adjacent said deflecting means, the angle of incidence of said beam on the lines of force of said field being at least 90 throughout substantially the entire deflection range of said device.

2. A beam deflection device, comprising: a beam source; target means for said beam; means interposed between said source and target for deflecting said beam in two dimensions toward desired positions on said target means; means establishing a field condition for accelerating said beam toward said target means; and means interposed between said deflecting and target means for establishing a field boundary generally normal to the path of the deflected beam and adjacent said deflecting means, the angle of incidence of said beam on the lines of force at said field boundary being at least 90 throughout substantially the entire deflection range of said device.

3. A beam deflection device, comprising: a beam source; target means for said beam; means interposed between said source and target for deflecting said beam in two dimensions toward desired positions on said target means, said deflecting means having a center of deflection; means establishing a field condition for accelerating said beam toward said target; means for establishing a field boundary adjacent said deflecting means and generally symmetrical with respect to said center of deflection, the angle of incidence of said beam on the lines of force at said field boundary being at least 90 throughout substantially the entire deflection range of said device,

4. A beam deflection device, comprising: a beam source; target means for said beam; means interposed between said source and target means for deflecting said beam in two dimensions toward desired positions on aid target means, said deflecting means establishing a deflection volume having a center of deflection; means establishing a field condition for accelerating said beam toward said target means; and means interposed between said deflecting and target means for establishing a field boundary adjacent said deflection volume and generally symmetrical with respect to the center of deflection, the angle of incidence of said beam on the lines of force at said field boundary being at least throughout substantially the entire deflection range of said device.

5. A beam deflection device of the character described in claim 4, wherein the said field boundary is normal to the path of said deflected beam throughout substantially the entire deflection range of the device.

6. In a beam deflection device: a beam source; a target; means for deflecting said beam toward desired positions on said target; means for establishing a field condition for applying an accelerating force to said dcflected beam, accelerating it toward said target, with the accelerating force acting substantially along the path of said deflected beam throughout the deflection range of said device; and a source of alternating electrical signal connected with said field condition for varying the intensity of said field condition for imparting linear velocity modulation to said deflected beam.

7. In a beam deflection device: a beam source; means for deflecting said beam to desired positions; means for establishing a field condition for applying an accelerating force to said deflected beam, said means including a pair of parallel surfaces, the accelerating force acting substantially along the axis of said deflected beam throughout the deflection range of said device; and a source of alternating electrical signal connected with said surfaces for varying the intensity of said field condition for imparting linear velocity modulation to said deflected beam.

8. In a beam deflection device: a beam source; means for deflecting said beam to desired positions; means for establishing a field condition for applying an accelerating force to said beam, said means including a pair of parallel surfaces, one of which is a grid, the accelerating force acting substantially along the path of said deflected beam throughout the deflection range of said device; and a source of alternating electrical signal connected with said surfaces for varying the intensity of said field condition for imparting linear velocity modulation to said deflected beam.

9. A beam deflection device of the character described in claim 8, wherein both of said parallel surfaces are grids.

10. The beam deflection device of claim 8, wherein one of said parallel surfaces is a grid and the other is a target for said beam.

11. An ultrashort beam deflection tube, comprising: a target of substantial surface area; an envelope having a face generally coextensive with said target, mounting and enclosing the target, the depth of said envelope being much less than the surface dimensions of said face, said envelope defining a cavity; a structure including a beam source comprising a cathode having a beam emissive surface and beam intensity control and shaping elements, beam deflection elements for deflecting the beam in two dimensions to desired positions end said target and a beam accelerating field control grid, said structure being carried by said envelope and extending into said cavity, said accelerating field control grid establishing a field boundary adjacent said deflection elements, the angle of incidence of said beam on the lines of force of said field being at least 90 throughout substantially the entire deflection range of said device.

12. A beam deflection device, comprising: a beam source; target means for said beam spaced along an axis from said source; means establishing a low potential zone adjacent said source; means establishing a high potential zone adjacent said target and spaced from said low otential zone, the projection of the spacing between said zones on said axis being small with respect to the spacing between the zones; means operatively associated with said low potential zone for deflecting said beam in two dimensions to desired positions on said target means; and grid means at said low potential and positioned between said deflecting means and said space, modifying the field con- El formation in said space, the angle of incidence of said beam on the lines of force of said field being at least 90 throughout substantially the entire deflection range of said device.

13. A beam deflection device, comprising: a beam source; target means for said beam; means establishing a low potential zone adjacent said source; means establishing a high potential zone adjacent said target and spaced from said low potential zone; means operably associated with said low potential zone for deflecting said beam toward desired positions on said target means, said deflecting means establishing a deflection volume in said low potential zone having a center of deflection; and an equipotential grid at said low potential interposed between said zones, adjacent said deflecting means and generally symmetrical with respect to the center of deflection, the angle of incidence of said beam on the lines of force of the high potential zone adjacent said grid being at least 90 throughout substantially the entire deflection range of said device.

14. A beam deflection device of the character described in claim 13, wherein said grid has a surface which is a portion of a sphere formed about said center of deflection.

15. A beam deflection device, comprising: a beam source; target means for said beam; means establishing a low potential zone adjacent said source; means establishing a high potential zone adjacent said target and spaced from said low potential zone; means operably associated with said low potential zone for deflecting said beam toward desired positions on said target means; and an equipotential grid at said low potential, having alternate solid portions and openings therein, interposed between said zones and closely adjacent said deflecting means, the cross sectional area diameter of the beam at said grid being greater than the area of said openings.

16. A beam deflection device of the character described in claim 15, wherein said beam diameter is several times the area of said openings.

17. In a beam deflection device: an envelope; mounting means in said envelope; a cathode having a surface for emit-ting a beam of electrons carried by said mounting means; a beam intensity control element carried by said mounting means; beam shaping elements carried by said mounting means; a target for said beam in said envelope; means establishing a low potential zone in said envelope adjacent said mounting means; means establishing a high potential zone in said envelope adjacent said target and spaced from said low potential zone; a member of insulating material carried by said mounting means in said low potential zone and having conductive areas thereon for the application of electrical signals to establish a beam deflecting field; and a grid carried by said mounting means, at a low potential, interposed between said zones and immediately adjacent said deflecting beams, the angle of incidence of said beam on the lines of force of the high potential zone adjacent said grid being at least 90 throughout substantially the entire deflection range of said device.

18. The beam deflection device of claim 17, wherein said member of insulating material is tubular and has a generally parabolic surface.

19. A beam deflection device, comprising: a beam source; target means for said beam; means for deflecting said beam to desired positions on said target means; means establishing a field condition for accelerating said beam toward said target means; and a mesh grid modifying said field condition adjacent said deflecting means, the angle of incidence of said beam on the lines of force of the field at said grid being at least 90 throughout substantially the entire deflection range of said device.

20. An expanded-sweep, beam deflection device, comprising: a beam source; target means for said beam; means for deflecting said beam in two directions to desired positions on said target means; means establishing a field condition for accelerating said beam toward said target means; and a mesh grid modifying said field condition be- 16 tween said deflecting means and said accelerating means, the angle of incidence of said beam on the lines of force of said field being at least throughout substantially the entire deflection range of said device.

21. An expanded-sweep, cathode-ray tube, comprising: an electron beam source; a sensitized screen providing a target for said beam; means for deflecting said beam in two directions to desired positions on said screen; means establishing a field condition for accelerating said electron beam toward said screen; and a mesh grid modifying said field condition adjacent said deflecting means, the angle of incidence of said electron beam on the lines of force of said field being at least 90 throughout substantially the entire deflection range of said tube.

22. A cathode-ray tube having means for generating a cathode-ray beam and for directing the same along a predetermined path to a viewing screen for use in a display system which includes a signal-actuated deflection means spaced from the viewing screen for establishing deflecting fields within the tube for scanning the beam in first and second mutually perpendicular directions, with said deflection means having an effective deflection center, said tube including radially symmetrical electrostatic lens means constructed to produce a divergent magnifying field within the tube, said electrostatic lens means including an electrode composed of finely apertured conductive material located between the effective deflection center and the screen in the path of the beam and at least partially transparent to the electrons thereof, and an annularmember along the path of the beam beyond said electrode and adapted to be maintained at a potential higher than that of said electrode, whereby said lens means produces a symmetrical field to refract the beam divergently with respect to the predetermined path and magnify the scan thereof.

23. In a display system which includes a cathode-ray tube having an electron gun for directing a cathode-ray beam along a predetermined path from an electron source to a viewing screen, and deflection means located between the electron source and the viewing screen for deflecting the beam to scan the screen and having an effective deflection center, electrostatic negative lens means located between the effective deflection center of said deflection means and the viewing screen for producing within the tube an electrostatic field which is radially symmetrical about the predetermined path of the beam, said electrostatic field having components acting radially outward from the predetermined beam path such that the effect of said lens means is to refract the beam divergently with respect to the predetermined path and magnify the scan thereof.

24. In a display system which includes a cathode-ray tube having an electron gun for directing a cathode-ray beam along a predetermined path from an electron source to a target area, and which further includes deflection means for establishing deflecting fields located between the electron source and the target area for scanning the cathode-ray in a first direction perpendicular to the predetermined path thereof and in a second direction perpendicular to the first direction, said deflection means having an effective deflection center, electrostatic negative lens means for producing a magnifying field located betweeen the effective deflection center of said deflection means and the target area, said magnifying field being radially symmetrical and having a divergent refractive effect on the cathode-ray beam for magnifying the scan thereof in both the first and second directions.

25. A cathode-ray tube having means for generating a cathode-ray beam and for directing the same along a predetermined path to a viewing screen for use in a display system which includes signal-actuated deflection means spaced from the viewing screen for establishing deflecting fields within the tube for scanning the beam in first and second mutually perpendicular directions, said tube including radially symmetrical divergent electrostatic lens means located to produce a magnifying field within the tube between the deflection means and said viewing screen, said electrostatic lens means including a field terminating elect-rode composed of finely apertured conductive material in the path of the beam and transparent to the electrons thereof, whereby the effect of said divergent lens means is to refract the beam divergently with respect to the predetermined path and magnify the scan thereof.

26. A cathode ray tube comprising a vacuum-tight envelope having a neck portion, a faceplate portion, and an interjacent cone portion; means disposed within said neck for projecting an electron beam toward said facelate through a beam deflection region to scan said beam over said faceplate portion, a screen electrode on said faceplate, dome-shaped grid elect-rode means disposed adjacent said deflection region and between said region and said screen for electrically shielding said region from said screen, the open side of said dome facing said deflection region, and a conductive coated electrode on said cone portion, said dome-shaped grid electrode being contoured to provide in cooperation with said conductive coating electrode a supplemental radial deflection electrostatic field.

27. A cathode ray tube comprising a target electrode, means for projecting an electron beam toward said target electrode through a beam deflection region to scan said beam over said target, terminal means for applying a high positive potential to said target, multi-apertured grid electrode means disposed adjacent said deflection region between said region and said target in the path of said beam for electrically shielding s-aid region from said high positive target potential, hollow cylindrical electrode means disposed adjacent said multi-apertured grid electrode means and between said multi-apertured grid electrode means and said electron beam projecting means, and means for mounting said multi-apertured grid electrode and said hollow cylindrical electrode means in mutual electrical insulated relation whereby said hollow cylindrical electrode means may be electrically biased relative to said multi-apertured grid electrode.

28. In a display system which includes a cathode-ray tube having an electron gun for directing a cathode-ray beam along a predetermined path from an electron source to a viewing screen, and deflection means located between the electron source and the viewing screen for deflecting the beam to scan the screen and having an effective deflection center, electrostatic negative lens means located between the effective deflection center of said deflection means and the viewing screen for producing within the tube an electrostatic field which is radially symmetrical about the predetermined path of the beam, said electrostatic field having components acting radially outward from the predetermined beam path such that the effect of said lens means is to retract the beam divergently with respect to the predetermined path and magnify the scan thereof.

29. A cathode-ray tube which has a viewing screen and an electron source for directing a beam toward the viewing screen, and which is adapted for use with deflection means for establishing deflecting fields within the tube about an effective deflection center located between the electron source and the viewing screen for deflecting the beam to scan the same across the screen, said tube including electrostatic magnifier means providing a radially symmetrical divergent electron lens located between the position of said deflection center and the viewing Screen for magnifying the scan, and means providing focusing fields within the tube of a sense and magnitude to compensate for the divergent effect of said magnifier means on the beam and thereby focusing the beam on the screen.

30. A cathode-ray tube which has a viewing screen and an electron source for directing a beam toward the viewing screen, and which is adapted for use with deflection means for establishing deflecting fields within the tube having an effective deflection center located between .the electron source and the viewing screen for deflecting the beam t-o scan the same across the screen, focusing means associated with the electron source providing a positive electron lens located between the electron source and the position of the effective deflection center for focusing the beam, and mea-ns providing a radially symmetrical negative electron lens located between the effective deflection center of said deflecting fields and the viewing screen for magnifying the scan, said positive electron lens having suflicient convergent strength to compensate for the divergent effect of said negative lens on the beam so that the beam is focused on the viewing screen.

31. In a display system which includes a cathode-ray tube having a viewing screen and means including an electron source for directing the beam to the viewing screen, and deflection means for establishing deflecting fields located within the tube between the electron source and the viewing screen for deflecting the beam to scan the screen, the combination including, focusing means providing a focusing field located within the tube between the electron source and the deflecting fields for converging the beam, and electrostatic means for providing a radially symmetrical divergent electron lens within the tube between said deflecting fields and the viewing screen for magnifying the deflection of the beam, said electrostatic means including a field terminating electrode located in the path of the beam and transparent to the electrons thereof so that the effect of said electron lens means is to refract the beam and magnify the scan thereof, said focusing field having sufficient convergent strength to compensate for the divergent effect of said magnifying electron lens on the beam so that the beam is focused on the viewing screen.

32. A cathode-ray tube having an electron gun for directing a cathode-ray beam along a predetermined path from an electron source to a viewing screen, said tube being adapted for use with deflection means for establishing deflecting fields within the tube having an effective deflection center located between the electron source and the viewing screen for deflecting the beam to scan the same across the screen, said tube having a radially symmetrical lens structure providing a radially symmetrical divergent electron lens located between the position of the deflection center and the viewing screen and effective to magnify the scan of the beam, at least part of said lens structure being located in the path of the beam and being at least partially transparent to the electrons of the beam, and means establishing focusing fields within the tube effective to compensate for the divergent effect of said electron lens on the beam and thereby focusing the beam on the viewing screen.

References Cited by the Examiner UNITED STATES PATENTS 2,114,572 4/38 Ressle-r 313-78 X 2,153,949 4/39 Varian 313-76 2,158,314 5/39 Korshenewsky 313-78 X 2,225,455 12/40 Klauer 313-77 2,315,367 3/43 Epstein 313-92 X 2,498,354 2/50 BOcCiarelli 250-161 2,617,077 11/52 Schlesinger 313-78 X 2,632,864 3/53 Hunter 313-76 X 2,728,025 12/55 Weimer 313-925 X 2,732,511 1/56 Dichter 313-181 2,770,748 ll/56 Schlesinger 313-78 2,793,319 5/57 Nunan 313-925 X 2,795,729 6/57 Gabor 313-78 X 2,795,731 6/57 Aiken 313-92 2,808,526 10/57 Davis 313-71 2,813,224 1l/57 Prancken 313-925 X 2,821,656 1/58 Foster 313-92 (Other references on following page) References Cited by the Applicant UNITED STATES PATENTS GEORGE N. WESTBY, Primary Examiner.

1 3 UNITED STATES PATENTS 4/58 Hamlet 313-76 3/59 T116116 31510 2 150 159 FOREIGN PATENTS 2,176,199 10/ 37 Great Britain 5 1 2 73 5 956 5/43 Great Brltam. 91 6/36 France. 2755413 1/ 36 Germany. 42 8/53 Germany. 10 2892962 2/ 43 Italy. 9/37 Switzerland. 8/45 Switzerland.

RALPH G. NILSON, Examiner.

Claims

1. A BEAM DEFLECTION DEVICE, COMPRISING: A BEAM SOURCE; TARGET MEANS FOR SAID BEAM; MEANS FOR DEFLECTING SAID BEAM IN TWO DIMENSIONS TO DESIRED POSITIONS ON SAID TARGET MEANS; MEANS ESTABLISHING A FIELD CONDITION FOR ACCELERATING SAID BEAM TOWARD SAID TARGET MEANS; AND MEANS MODIFYING SAID FIELD CONDITION ADJACENT SAID DEFLECTING MEANS, THE ANGLE OF INCIDENCE OF SAID BEAM ON THE LINES OF FORCE OF SAID FIELD BEING AT LEAST 90* THROUGHOUT SUBSTANTIALLY THE ENTIRE DEFLECTION RANGE OF SAID DEVICE.