US3042832A

US3042832A - High-sensitivity cathode-ray tube

Info

Publication number: US3042832A
Application number: US806886A
Authority: US
Inventors: Harvey M Owren
Original assignee: ABTRONICS Inc
Current assignee: ABTRONICS Inc
Priority date: 1959-04-16
Filing date: 1959-04-16
Publication date: 1962-07-03
Anticipated expiration: 1979-07-03
Also published as: NL250540A; DE1222170B; GB913475A

Description

July 3, 1962 H. M. o wREN HIGH-SENSITIVITY CATHODE-RAY TUBE Filed April 16. 1959 JNVENToR. HAP/ffy wPf/v rroPA/iy Y 3,042,332V mon-sartsrrmrr cArHonr-RAY TUBE Harvey M. wren,

tronics, Inc., fornia Filled Apr. 16, 1959, Ser. No. 866,886

11 Claims. (Cl. 315-18) Livermore, Calif., assigner to Ab- Liverrnox'e, Calif., a corporation of Cali- The present invention relates in general to an improvement in the sensitivity of cathode-ray tubes, and

more particularly to electrode means for a cathode-ray tube operating to additionally deilect and accelerate an electron beam therein to the end of providing improved tube sensitivity and magnifica-tion while preserving the beam focus therein.

It is highlyv desirable in any application of cathoderay tubes to provide a maximized beam deflection in the tube tothe end of providing a sweep of extended length and also it is highly desirable to provide .a maximum screen brilliance. Although it is possible to attain in part these objectives by conventional means such as increasing the normal tube deecting voltage or current yet such conventional approaches are limited in that same generally impose undue requirements on auxiliary tube circuitry. Thus, for example, requisite voltage variations and power delivery that would be necessary for such approaches wou-ld lbe excessive sol as to preclude widespread usage thereof. Further, the additional acceleration of cathode-ray tube beams imposes in itself a serious ditiiculty. Full beam acceleration to very high beam energy prior to beam deiiection has been found to be undesirable because of difficulties encountered in the deecting system, i.e., the problem of achieving desired deection and control of the beam. `Post-deflection acceleration, i.e., acceleration of the beam after deflection, While overcoming the above-noted diiiiculties raises other problems in that image distortion results. While postdeilection acceleration systems are known and used, the tube resolution in such instances suifers thereby so that systems of that type are inherently limited, at least in their presently knownform. Furthermore, conventional post-acceleration methods are directed to preserving the deflected beam `direction so as to be applicable only Vin connection With increasing beam energy without improvement of tube sensitivity.

The present invention is directed to overcoming the above-noted difculties encountered in the cathode-ray tube ant as well as to the provision of other advantages in such art. It is contemplated Aby the present invention that there shall be provided within a cathode-ray tube and following the deflection means thereof, auxiliary or secondary beam accelerating electrodes which are so formed and disposed as to define, yby appropriate potentials impressed therebetween, the electron beam accelerating and deflecting fields. Contrary to conventional post-deflection acceleration systems previously employed in Ithe cathode-ray tube art, the present invention operates to additionally accelerate an electron beam and to magnify the original controlled deilection thereof without introducing image distortion. This is herein accomplished by the provision of spherical electric yfields wherein beam acceleration is accomplished in the direction of deiiection rather than parallel to the tube axis. In this manner the present invention is capable not only of further accelerating cathode-ray tube beams but also of further deflecting same in a uniform manner so that the resultant beamV impinging upon the cathode-ray tube Screen is additionally radially deflected to thereby expand or magnify the trace appearing uponV the screen and at the same time lto further energize the beam so as to intensify the magnified trace on the screen. The

the end of the chamber and an 3,642,832 Patented July 3., 1962 fire 2 foregoing is accomplished without in any way detracting from the trace resolution or in any way distorting the image or display.

In accordance' with the foregoing it is an object of the present invention to provide the cathode-ray tube Vof improved sensitivity.

It is another object of the present invention to provide a cathode-ray tube with secondary or auxiliary beam deflection means for maximizing magnification of ythe tube display. f

It is a further object of the present invention to Aprovide a cathode-ray tube improvement including means producing post-deection beam acceleration without image distortion. Y

It is yet another object of the present invention to provide an improved cathode-ray tube including means further accelerating the electron beam therein in a deected direction for increasing beam energy while at the same time magnifying beam deiiection.

Various other advantages and possible objects of theV present invention will become apparent to those skilled in the art from the following description and drawing wherein there are illustrated several preferred embodiments of the present invention. Although only particular preferred embodiments of this invention are herein illustrated and described, it is not intended to limit the invention -by the terms thereof but instead reference is made to the appended claims for a precise delineation of the true scope of the present invention.

The invention is illustrated in the accompanying drawing, wherein:

FIG. 1 is a schematic illustration of a cathode-ray tube including the improved accelerating and dellecting means of the present invention;

FIG. 2 is a schematic illustration of a portion of a cathode-ray tube including an alternative embodiment of the present invention;

FIG. 3 is a schematic illustration of a portion of a cathode-ray tube including a further embodiment of the present invention; and

FIG. 4 is a schematic illustration of a portion of a cathode-ray tube including yet another embodiment of the present invention. i

Considering now the present invention in some detail as regards the preferred embodiments thereof illustrated, and referring to FIG. 1 of the drawing, there Will be seen to be illustrated in schematic form therein a cathoderay tube 11 including an evacuated envelope 12. In conformity with conventional cathode-ray tube practices, the envelope 12 defines an expanded chamber 13 at one end thereof with a cathodoluminescent screen 14 disposed at elongated neck or tube 16 extending from this screen 14 to house at the opposite end of the neck an electron beam source17. This electron beam source 17, upon appropriate and conventional energization, not shown, is adapted to produce an electron beam and to direct same along an axis 20 of the cathode-ray tube which intersects the tube screen 14 at the center thereof. Along the tube axis from the electron beam source 17 there is provided a primary electron lens 18 Which may, as illustrated, include a plurality of elements spaced along the tube axis and through which the electron beam is adapted vto pass for accelerating and focusing same. Following the primary lens system 18 there are provided deection means 19 spaced along the tube axis and including horizontal and vertical deiiection means such as the pairs of plates illustrated. It Will be appreciated of course that either electrostatic or electromagnetic deflection means may be employed in conventional manner in the cathode tube modified by the present invention and also that conventional energization of the tube elements is intended. An electron beam 21 emitted from the beam source 17 and passing axially through the primary electron lens 18, is radially defiected in passing through the deflecting means 19 and such deflection is normally accomplished in such a manner as to impart desired intelligence to the beam, such as, for example, by the application in an electrostatic deflecting system of suitably modulated defiecting potentials. The beam 21, upon emergence from the deflecting means and passage through the chamber 13, is deflected to radially separate, as regards consecutive beam portion, to thereby impinge upon the screen 14 at successive spaced points to provide a trace thereon. Considering a single beam portion, for simplicity of explanation, there is indicated in FIG. 1 by the dotted line 22 the path followed by such a beam portion receiving a particular radial deflection in passage through the deflecting means 19 in a conventional cathode-ray tube. As noted above, conventional cathode-ray tubes, as described to this point, are limited in the maximum beam energy that may be provided, for inasmuch as beam accelerat-ion is normally accomplished' in the primary electron lens or source, such acceleration is prior to beam deflection and consequently with too high a beam energy or velocity as a result of excessive beam acceleration the deflecting means become unable to provide the desired beam deflection. This results from the limited time in which the electron beam is subjected to the deflecting forces of the deflection means and such deflection time will be seen to be a direct function of the beam velocity. As regards sensitivity, conventional cathoderay tubes are limited by the fact that large beam deflections require large spacing between deiecting plates so that the defiected beam will not strike same and with increased spacing between deflecting plates, there results a lesser effect upon the beam by any particular potential applied to the plates. The present invention provides close spacing of the deflecting plates so that only very small deflecting potentials are required.

The present invention provides means for additionally accelerating electron beams in a cathode-ray tube after controlled deflection thereof and for magnifying the defiecton without distortion of the resultant display. To this end there is herein provided, as shown in FlG. l, a first electrode 26 disposed symmetrically about the beam axis adjacent the deflecting means 19 and toward the screen 14 therefrom. This first electrode 26 defines a semi-spherical surface and may to this end include a spherical portion 27 facing the screen 14 and including or defining a beam-transparent section of the electrode. This transparent portion of the electrode 26 is disposed immediately about the tube axis so as to admit of passage of the beam through the electrode. As shown in FIG. 1, the electrode 26 is formed as a hollow cylinder having a spherical end directed toward the screen 14 with an opening 28 through such end for the passage of an electron beam therethrough. This spherical electrode portion 27 is disposed with the center 29 of the spherical surface located upon the tube axis. Displaced axially of the tube from the first electrode 26 is a further electrode 31. This further electrode 31 also defines a spherical surface as by a semi-spherical end portion 32 formed on a radius of curvature substantially greater than that of the spherical portion 27 of the electrode 26, but however having the same center 29. The electrode 31, which is preferably radially displaced from the tube axis so as to be disposed adjacent the sides of the envelope 12, is also provided with a central beam transparent portion which, as is illustrated in FIG. 1, comprises a large opening 3'3 which may in fact approach the size of the tube screen 14. inasmuch as the electron beam is radially deflected in passage through the electrodes of the present invention, a substantial beam opening is required in the electrode 31 in order that the beam 21 will not impinge upon the electrode. Intermediate the

electrodes

26 and 31 there may be provided a further electrode 36 formed with a spherical surface 37 having the same center 29 as the spherical surfaces of the other electrodes and having a radius of curvature intermediate of the radius of curvature of the electrode 36 and electrode 31. Similar to the above-described

electrodes

26 and 31, the intermediate electrode 37 is provided with a central beam.v transparent portion 38 disposed symmetrically about the tube axis and providing an unobstructed passage for the beam 21 through the electrode. In the illustrated ernbodiment, the intermediate electrode 36 is disposed equidistant between the electrodes 26 and '31 although other disposition thereof is possible. Suitable physical mounting of the electrodes within the envelope may be accomplished in accordance with conventional tube practice and is thus not illustrated. Also the electrode 31 may be formed upon the tube envelope.

Electron beam acceleration and deflection is accomplished by the above-described electrodes through the application of suitable potentials to these electrodes for forming defiecting and accelerating electric fields in the beam path. Electrical potentials are applied between the electrodes in such a manner as to maintain the first electrode 26 at a relatively negative potential with respect to the electrode 31 and further to maintain the intermedia-te electrode 36 at an intermediate potential of a value dependent upon the physical location of same between the other two

electrodes

26 and 31. Electrical connection is made, as by means of

conductors

41, 42 and 43, from the

electrodes

26, 36 and 31, respectively, into connection at appropriate points upon such as a voltage dividing resistor 44 connected across a power supply, illustrated as a battery 46.

The intermediate electrode 36 is maintained at an appropriate potential to further establish the spherical deflecting and accelerating field. As illustrated, the electrode 36 is maintained at a potential about 0.7 of the total voltage between electrodes 26 aud 31, as by con-g nection to the center of a logarithmic resistor 44. Any desired number of electrodes may be employed to establish the desired spherical field configuration and appropriate potentials applied thereto for this purpose, however, somewhat different potentials may also be employed in order to distort the field to produce certain desired results such as compensation for some other cause` of distortion or suitable direction of the beam onto a planar screen.

By the foregoing electrical connection of the

electrodes

26, 31 and 36, there is established an electric field intermediate the `deflecting means 19 Iand screen 14 of the cathode-ray tube wherein the field lines are normally spherical -about the tube axis. Thus, between the

electrodes

26 and 31 there is established an electric field having lines of equal potential which lie upon spheres having the electrode center 29 as the center thereof and, 'in effect, radiating outward therefrom. The intermediate electrode 36 operates only to further define this field, particularly wherein the physical separation of the

electrodes

26 and 31 is substantial. It will be seen from a consideration of the electric field established by the electrodes of the present invention, that there is provided thereby a potential gradient `axially of the tube and radially thereof. With the electrode 31 closest to the tube screen 14 maintained at a relatively positive potential with respect to the electrode 26 disposed adjacent to tube deflecting `means 19, this potential gradient operates to urge electrons within the field axially of the tube toward the screen 14 and radially of the tube outward of the axis thereof. Consequently, an electron beam fdefiected by the deflecting means 19 and passing through the electrode 26 enters a spherical electric field of substantial extent wherein the potential gradient is of proper polarity to urge electrons radially outward of lche tube and 4also to urge electrons toward the screen 14. With ythe field established by the electrodes of the present invention, a deflected electron beam is thereby accelerated toward the screen 14 -While at `the same time being deflected radially outward of the tube axis. `In eEeot, electron acceleration occurs in the direction of deflection so that consequently no distortion of the beam display results, -as would be the case with electric fields established normal to the tube axis and extending perpendicularly therefrom. In addition to the general case of exactly spherical fields, there may herein be readily introduced such variations in the elds as are necessary to compensate for distortions that otherwise result in the display from other causes. This is herein accomplished by variations in the shape ofthe intermediate electrodes or in the potentials applied thereto.

A modification of the present invention is illustrated in part in FIG, 2 wherein there is shown the electrodes 26, 3-1 and'36 of the present invention substantially as illustrated and employed in FIG. l, `described above.v The modification herein illustrated is that of providing a continuation of each of the electrodes into -a complete sphere o-r semi-spherical surface about the tube axis. Such electrode continuation is herein made in the form of electronic grids 51, `52 and 53, enclosing the

electrode openings

2S, 38 and 33, respectively. These electronic grids are disposed, as above stated, upon a spherical surface which is, in the case of each electrode, a continuation of the electrode curvature. Additionally, these grids VSi, 52 and 53 are formed in a conventional manner as a very high permeancel structure, as for example, of wire mesh. Stated otherwise, each of the grids has a high Itransmissivity or transparency for electrons and are thus formed with a maximum area of openings therein and a minimum area of grid wires or elements. With the grids having a high transmission factor for the electron beam only a very small proportion of the beam is intercepted thereby so that problems of grid heating or beam attenuation or minimized. The function of the grid structures illustrated in FlG. 2 is to Afurther delineate the electric field established by the electrodes of the present invention. 'Ilhere is illustrated in FIG. 2 by the lines 54 a representation of equipotential lines resulting from the above-noted potentials applied to the grids. It will be seen that these lines 54 have the same radius of curvature as the electrodes and -as each other inasmuch as each lies on circles having the common center 29 of the electrodes. Also illustrated in FG. 2. are lines of force of the electric field established by the electrodes and such are thereby shown as dashed lines 56 which will be seen to emanate uniformly from the first electrode 26 radially outward of the tube axis and directed toward the tube screen with the focal point of the lines being the center of curvature 29 of the electrodes. It will be appreciated that electrons entering'the field established between the `electrodes 26 and 3l of the present invention will tend to follow the lines of force 56 illustrated in FlG. 2 and that also electrons following such lines of force Iwill be accelerated along same inasmuch as the positive terminal ofthe field is disposed adjacent the screen 14 of the tube. Consequently it is clear from ia study of PEG. 2 that an electron beam passing through the rst electrode 26 and entering the electric field established by the electrodes will in fact be radially deflected While at the same time being accelerated in the direction that the beam is traveling so that the electrodes thereby operate not only to further energize the beam but also `to radially deflect same -outwardly of the tube axis. The acceleration imparted to the beam by the field established with these electrodes is not parallel -to the tube axis, yand therefore does not operate to distort the display so that no reduced resolution accompanies the intensication.

A further embodiment of the present invention is illustrated in BIG. 3 of the drawing wherein a relatively inverted electrode system is illustrated. In this embodi- 6 ment of the invention there is provided a first semispherical electrode 6l having the center of curvature 62 thereof disposed upon the beam axis 20, but in this instance oriented to provide the convex electrode surface in facing relation to the cathode-ray tube deilecting means i9. This electrode 6l is disposed adjacent the deflecting means 19 of the cathode-ray tube and is provided with a central opening or electron beam transparent portion 63, about the tube `axis Ztl of suicient diameter to accommodate the deflected beam 21 passing therethrough. An additional electrode 64 is provided as a semi-spherical element'having the same center 62 as the electrode 61 and having a much smaller radius of curvature than that ofthe prior electrode 61. This second electrode 64 is disposed intermediate the first electrode 61 yand the tube screen 2,4 with the convex side thereof facing the concave side of the electrode 61 and has a -minute opening 66 therein about the tube axis 20 for the passage of an electron beam therethrough. As an additional portion `of this second electrode 64 there is preferably provided a diverging funnel or horn-shaped portion 67 directed toward the screen 14 and flaring outwardly toward same.

.As in the above described embodiments the spherical electrodes of the present embodiment are adapted .to establish therebetween a spherical electric field for deflecting and accelerating an electron beam entering same. To this end the electrodes are connected to a suitable source of potential, herein illustrated as a battery 68, maintaining the first electrode 6l at a relatively negative potential with respect to the second electrode 64.

It will be appreciated from a consideration of the electrostatic field configuration established by the relative potentials of the electrodes 61 and 64 that an electron beam 21 entering the electrode field region of the embodiment illustrated in FIG. 3 will undergo a deflection which will, in fact, reverse the beam dellection radially of the tube. Lines of force of the deflecting electric field will be seen to converge toward the screen 14 rather than oppositely, as in the above described embodiments of the invention, and thus `the radial potential gradient acting upon `an electron 4beam entering the held urges the beam toward the axis of the tube so that the beam is in fact redirected. The beam deflection produced by the spherical accelerating and dellecting fields of this embodiment of the invention is such as to cause the beam to cross the tube axis and the 'resultant radial beam deflection is proportional to the original deflection but in excess thereof. It will be seen further that with the second spherical electrode 64 having a relatively small radius of curvature and also a relatively small beam opening 66 therein, that the electron beam is generally constrained to follow lines of force of the electric field and will be in fact focused through the electrode aperture 66 to pass generally through the center of curvature 62 of the electrodes and thence onward in a relatively field-free region within the funnel or horn 67 into impingement upon the screen 14. In this instance the second electrode 64 and funnel or horn 67 thereof may be electrically connected to the screen'14 Vso that there is in fact established an electric field free region through which the beam passes after entering the second electrode 64. Inrthe above described embodiments the electrode adjacent the screen of the cathoderay tube may also be electrically connected thereto. Here again in lthe embodiment of the present invention illustrated in FIG. 3 of the drawing, an electron beam 21 entering the'electric iield established between the electrodes of the present invention will experience an acceleration toward the screen 14 along the deflected path of the beam while at the same time experiencing a radial potential gradient oper-ating to further radially deflect the beam. Thus in this embodiment the same result pertains in that following conventional beam deflection of :the cathode-ray tube there is established a spherical electric field in the beam path which operates to further accelerate and deflect the electron beam whereby such beam impinges upon the cathode-ray tube screen at an increased energy and with an increased radial deflection.

The improved electron beam accelerating and deflecting system of the present invention is also adapted to various other applications as, for example, the one illustrated in FIG. 4 of the drawing. Therein there is shown an electrode system including first, second and third electrodes 71, 72 and 73 disposed in the named order between cathode-ray tube deflecting means 19 and screen 14. As in the embodiments of FGS. 1 and 2, the electrodes 7l, 72 and 73 are herein formed `as spherical surfaces, or at least semi-spherical surfaces, with a common center disposed on the tube axis and with the electrodes disposed symmetrically about the axis. The electrodes are provided with electron beam openings therethrough of progressively increasing size toward the cathode-ray tube screen in order to afford adequate passageway for an electron beam traversing the tube to the screen thereof.

As a departure from the above teaching, there is provided in this embodiment a thin sheet or film 74 across the opening in the first electrode 71 disposed adjacent the deflecting means 19. This iilm 74 lies upon the spherical surface of the electrode to define with the electrode the semi-sphere thereof. Additionally, this film 7e is formed of a material that is a good emitter of secondary electrons upon bombardment by primary electrons. More particularly the film 74 is adapted to produce from the convex side thereof a plurality of electrons for each electron impinging the concave side of the film with such emission occurring directly through the film from the point of impingernent of the primary electron. t will thus be seen that a deflected primary electron beam Z1 of the cathode-ray tube strikes the film 74 upon the concave side thereof to produce thereby an electron beam 76 formed of secondarily emitted electrons from the convex side of the film 74, which secondary electrons are then further-accelerated by a spherical field established by the electrodes 71, 72 and 73. As noted above, electrons are secondarily emitted from the convex side of the film 74 directly opposite the point of impingement of a primary electron on the concave side thereof so that in effect the secondary electron beam 76 forms `a continuation of the primary beam but is composed of a much greater number of electrons. Suitable electrical connections from the electrodes 71, 72 and 73 to appropriate points on a voltage dividing resistor 77 connected across a power supply, illustrated yas a battery 78, serve to establlish a spherical electric field symmetrically about the tube axis 20 in the same manner as described above in relation to FIG. 1. It will be seen that the spherical magnetic field established by the electrodes 71, 72 and 73 of FIG. 4 operate in the same manner as described above in connection with PIG. 1 to provide an additional electron beam acceleration to thereby materially increase the beam energy and further to additionally radially defleet the beam in proportion to the amount of the original ydeflection accomplished in the deflecting means 19 of the cathode-ray tube.

A further and material advantage of the embodiment of FIG. 4 is that of providing a substantial increase in the beam current by the utilization of a secondary emitter' in the beam path. It is herein contemplated that the primary electron beam of the cathode-ray tube need not be of a high current value, for the multiplication afforded by the secondary emitter 74 is sumcient to provide a resultant or secondary beam 76 having a current density greatly in excess of those available from conventional cathode-ray tubes.

An improved cathode-ray tube constructed in accordance with the principles of the present invention has, during operation and test, proven to have a sensitivity some ten times that of conventional cathode-ray tubes. A suitable ratio of radii of first and last electrodes has been found to lbe 5:1. Additionally, an advantage of the present invention lies in the fact that deflection sensitivity may be made materially higher even with a high final beam energy as the deflection is largely independent of the final potential. It is also to be noted in connection with the present invention that additional focusing of the electron beam may be provided by appropriate control of the relative potential between the electrode system and the electron gun assembly, including the `abovedefined electron beam source and primary electron lens.

What is claimed is:

1. A high-sensitive cathode-ray tube comprising an electron beam source, deilecting means for controllably deilecting an electron beam therefrom, a screen for intercepting said beam, and a plurality of electrodes disposed along said beam path intermediate said deflecting means and said screen and establishing substantially semi-spherical electric fields symmetrically about the tube axis with lines of force radiating from a point which is disposed on said tube axis and is displaced from said deflection means for further deflecting said beam radially outward of the tube axis to spread same upon said screen.

2. in a cathode-ray tube having means establishing an electron beam along an axis thereof and means controllably deilecting the beam from said axis to impinge at controllable points on a tube screen displaced axially of the tube: the improvement comprising at least two electrodes spaced along the tube axis intermediate the deflecting means and screen, said electrodes being disposed symmetrically about the tube axis and each defining thereby, including projections thereof, a semi-spherical surface with each having a common center of curvature displaced 'along the tube axis from the beam deflection means of the tube; and means applying a potential difference between said electrodes to maintain the one nearest said screen positive with respect to the other for establishing beam eflecting and accelerating fields.

3. Electron beam deilecting and accelerating means for a device producing an electron beam and controllably deiiecting same to direct the beam upon a screen displaced axially of the device from the point of beam deflection, and comprising at least two electrodes having concentric semi-spherical shapes and each disposed symmetrically about the axis of said device, said electrodes each having a portion about the axis of said device which is transparent to said electron beam, and means maintaining upon said electrodes a potential of decreasing positive polarity from the electrode adjacent said screen to the one adjacent the beam deflection for establishing spherical electric fields in the path of said beam, said fields having coincident centers of curvature displaced along the tube axis toward said screen from said controllable beam deflection to further deflect said beam radially outward of the device and to accelerate same in such deflected direction whereby the beam impinges upon said screen at radially displaced positions without beam defocusing.

4. Means claimed in claim 3 further defined by said electrodes comprising a pair of concentric segments of spheres of different radius disposed symmetrically about said axis with the center of curvature disposed thereon and the one with the larger radius disposed adjacent said screen with the convex side thereof facing said screen.

5. Means 'claimed in claim 3 further defined by said electrodes each having a central grid portion of high transparency for electrons and each of said portions being disposed symmetrically about the axis of said device.

6. An improved cathode-ray tube comprising an electron beam source projecting an electron beam along an axial path, deflecting means adapted for controlled energization to radially deflect an electron beam directed therethrough, a screen displaced from said deflecting means along the beam axis and disposed to intercept said beam, a first electrode having a centrally apertured spherical portion disposed symmetrically about said beam axis adjacent portions therein said deflecting means, a second electrode disposed between said first electrode and said screen and having a centrally apertured spherical portion disposed symmetrically about said beam axis concentrically with the spherical portion of said first electrode, the spherical portions of said electrodes having the centers of curvature thereof disposed on the tube axis toward said screen from said deflectingy means, and means maintaining said second electrode at a positive potential with respect to said first electrode for establishing a radially diverging electron accelerating field whereby an electron beam traversing same is accelerated and deflected radially outward of the beam axis into out- Wardly displaced impingement upon said screen.

v 7. Beam deflection and acceleration means for a cathode-ray tube including a beam source directing a beam along an axis through the beam deflection means toward a screen, and comprising a pair of concentric semi-spherical electrodes spaced along said axis between said deflecting means and screen with each having beam transparent about said axis and adapted to have a potential impressed therebetween with the one nearest said screen maintained at a relatively positive potential with respect to the other for establishing beam accelerating and deecting fields diverging from a point on said axis displaced from said deflecting means toward said screen and operating substantially uniformly upon an electron beam passing at any deflection therethrough.

8. Beam deflection and acceleratoin means as defined in claim 7, further defined by the first of said electrodes having a Vgreater radius of curvature than the second and disposed on the opposite side of the second electrode from said screen, said iirst electrode having a large beam transl 10 parency for electron beams to define spherical electric fields shaped about the axis of the tube.

10. Beam deflecting and accelerating means for a cathode-ray tube having an electron beam source directing a beam axially of the tube toward a tube screen through deliecting means operable to controllably radially deiiect the beam, and comprising a plurality of electrodes spaced along the tube axis between said defiecting means and said screen with each of said electrodes defining a semi-spherical surface disposed symmetrically about the tube axis, said semi-spherical electrode surfaces being concentric and parallel and having coincident centers of curvature displaced along /the tube axis from said defiecting means, and said electrodes being adapted to have impressed therebetween electrical potentials of increasingly positive polarity toward said screen to establish uniformly diverging electron beam accelerating fields for focusing said beam at radially displaced points on the screen.

11. Beam deflecting and accelerating means as claimed in claim 10, further defined by one of said electrodes disposed closest to said deflecting means having a portion of parent portion therein, and said second electrode having a minute beam transparent portion therein through which the beam is focused by fields established 1between the electrodes. Y

9. Beam defiecting and accelerating means as claimed in claim 7 further delined by the beam transparent portion of said electrodes comprising electrical grids of high transthe spherical surface defined thereby intercepting the tube axis, said portion being formed of a sheet of secondarily emissive material producing on the side facing said screen a plurality of electrons for each electron of said beam striking the opposite side at a point directly through the sheet therefrom.

References Cited in the le of this patent UNITED STATES PATENTS 2,114,572 Ressler Apr. 19, 1938 2,315,367 Epstein Mar. 30, 1943 2,827,592 Bramley Mar. 18, 1958 FOREIGN PATENTS 802,715 France June 13, 1936 473,675 Great Britain Oct. 18, 1937 553,466 Great Britain May 24, 1943 109,216 Sweden Dec. 7, 1943