US3192431A - Deflection system for cylindrical beam cathode ray tube - Google Patents

Description

June 29, 1965 R. A. FRYKLUND 3,192,431

DEFLECTION SYSTEM FOR CYLINDRICAL BEAM CATHODE RAY TUBE Original Filed May l2, 1951 5 Sheets-Sheet 1 l /fWfA/a/P ,foar/PT A. rey/a UND June 29, 1965 R. A. FRYKLUND 3,192,431

DEFLECTION SYSTEM FOR CYLINDRICAL BEAM CATHODE RAY TUBE` I original FiledMay 12, 1951 5 Sheets-Sheet 2 /M/EA/Tof? 19o/SERT A. Fy/rwA/ ATTO/MEV June 29,` 1965 R. A. FRYKLUND 3,192,431

i DEFLECTION SYSTEM FOR CYLINDRICAL BEAM CATHODE RAY TUBE Original" Filed May 12, 1951 3 Sheets-Sheet 3 46" so (/,PcE

United States Patent O 3,192,431 DEFLEC'HQN SYSTEM FR CYLINDRCAL BEAM CATHODE RAY TUBE Robert A. Fryhlund, deceased, late of Dedham, Mass., by Dorothy H. Fryldund, administratrix, Dedham, Mass., assigner to Raytheon Company, Lexington, Mass., a corporation of Delaware Continuation of application Ser. No. 226,033, May 12, 1951. This application June 29, 1961, Ser. No. 124,283 11 Claims. (Cl. 315-18) This is a continuation of application Serial No. 226,053, tiled May l2, 1951, now abandoned.

This invention relates to electron-discharge devices, and more particularly, to cathode-ray tubes.

In copending application Serial No. 75,479, filed February 9, 1949, which was issued as United States Letters Patent No. 3,058,027, granted October 9, 1962, there is disclosed a circular beam cathode-ray tube and system adapted to utilize such a tube.

The tube comprises a circular electron-emitting surface which has forty-eight individual grids, respectively, adjacent forty-eight different portions of the eleotron-emitting surface, each grid controlling electrons emanating from the portion of the electron-emitting surface adjacent thereto substantially independently of the remaining grids. Electrons emitted from the surface are controlled by the grids, and if passed thereby are accelerated toward a fluorescent target such that, if electrons are allowed to pass by all forty-eight grids, a substantially circular pattern will appear on the fluorescent target.

During passage between the grids and the fluorescent target, the electrons are controlled by focusing, accelerating and deflection electrodes which are all made up of circular elements. In the case of the focusing electrode, due to the circular configuration, good focusing may be obtained in a direction radially of the axis of the tube, but relatively poor focusing is obtained circurnterentially of the axis of the tube. Thus, the electrons controlled by each grid strike the target in the form of an elongated spot such that for certain designs the elongated spots overlap.

Furthermore, as the diameter of the circular pattern on the target is increased or decreased by application of the deflection volt-ages to the deection electrodes, the degree of overlap of the spots on the target varies.

This invention discloses means whereby the electrons striking the target electrode may be made t-o fall on a short Iarcuate path which will substantially touch but not overlap the short arcuate paths `of electron beams controlled by adjacent grids.

Briefly, this invention comprises the use of a magnetic field axially of the tube at a point between the defiecting electrodes and the target, said magnetic field having a high frequency cyclically varying component. The electrons from the cathode which are acted upon by each of the forty-eight grids are formed into forty-eight separate beams, each beam being acted on by a grid. The beams are focused in a circumferential direction by passing through forty-eight small apertures, respectively, in a plate which is positioned adjacent the grids, and which is adapted to have a suitable focusing potential applied thereto. As a result, the beams appear on the target electrode as spots arranged in a circular pattern when no magnetic field is applied. However, when a magnetic field is applied having a varying component and the spots are deflected radially by the detlecticn system, the component of motion of the electrons radially will be acted on by the axial magnetic field to produce an alternating motion circumferentially lon :the tar-get electrode thereby elongating each spot into an arc ofthe segment of the circular pattern.

By adjusting the magnitude of the magnetic field, the length of the segment produced by each spot may be adment.

justed until it substantially contacts adjacent segments, but does not overlap. As the spots are deflected to -a larger extent by the defiecti-on electrodes, the radial component of motion of the electrons in the magnetic iield will be greater, hence producing a greater elongation of the segments such that the segments will continue to substantially touch, but not overlap as the circle grows in size by increasing the deliection voltage applied tothe deflection electrodes. l

This invention further discloses that magnetic focusing may be used in place of electrostatic focusing, said magnetic focusing being accomplished, for example, by a coil surrounding the electron-discharge device such that application cf a current through the coil will produce a magnetic field axially of the discharge device. Electrons emitted axially of the tube will travel through the focusing magnetic field without being lacted thereupon since they will be parallel to the magnetic lines. However, electrons which are emitted in a direction not parallel to the Iaxis 0f the tube will be .acted on and caused .to spiral around the average path crossing the path of electrons which travel parallel to the magnetic field once every revolution.

By adjusting the magnetic focusing field, electrons may be caused to impinge on the target electrode at substantially the time when they cross the path of parallel electrons thereby reproducing a focused image of the electron-emitting surface on the target electrode.

Other :and further objects and advantages of this invention will become apparent as the description thereof progresses, reference being had to the accompanying drawings, wherein:

FIG. 1 illustrates a longitudinal, cross-sectional viewv of an electron-discharge device embodying this invention;

FIG. 2 illustrates a transverse, partially broken away cross-sectional view of `the electron-discharge vdevice shown in FIG. l; and

FIG. 3 illustrates a modification of the device shown in FIG. 2 wherein the electron beams are magnetically focused.

Referring now to FIGS. 1 and 2, there is shown an electron-discharge device comprising an evacuated envelope 10, one end of the interior of which forms a target electrode coated with a liuorescent compound 11 of any desired type. At the other end of the electron-discharge device is positioned an electron gun 12 which is adapted to produce forty-eight separate electron beams which are directed to the fluorescent coating 11 to produce a substantially circular path thereon. Electron gun 12 may he of any desired type, the one described herein being by way of example only.

As shown herein, electron gun -12 comprises la central ceramic support cylinder 13 which extends the length of the gun and is surrounded by the gun proper. Attached to the one end of cylinder 13 is a disk 14 which surrounds cylinder 13 coaxial therewith, and is attached thereto by any desired means, as, for example, by Sauerizen ce- Positioned in an annular recess in the surface of disk 14 which faces the ffuorescent coating 11 is a cathode structure 1S comprising an annular metallic channel member, the exposed surfaces of which are coated with electron-emissive material, and the interior of which contains a heater wire 16. The heater wire is connected to a pair of leadins which extends out through the base of the envelope 1t) at the other end thereof from the portion coated with the fluorescent material,

Extending across the recess in disk 14 slightly spaced from the electronemissive surface of the cathode 15 are forty-eight grids 17. Eachy of grids 17 comprises a pair of wires which extends radially from the axis of the tube across the annular recess in the disk 14, and is connected together at their inner ends. Grids 1'7 are rigidly held to disk 14, for example, by cement adjacent the annular recess in disk 1d. Each of thegrids 17 is connected to a separate lead-in 18 which extends out through the base of envelope 1t). Positioned on the opposite sides of grids 17 from the disk 14 is a metallic disk 19 which is spaced slightly from grids 17. Disk 19 has a plurality of apertures 2@ therein, each of the apertures being, respectively, adjacent a grid 17 at the point where it passes over the cathode 15. Apertures 2t? may be, for example, circular, and have a diameter on the order of the spacing between the wires of each of the grids 17. Disk 19 is supported with respect to disk 14 by insulating spacing blocks 21 and 22 which may be annular in form, and respectwely, adjacent the inner and outer edges of disks 14 and 19.

Positioned on the opposite side of disk 19 from the grids 17 is an electrostatic focusing electrode structure 23 which, as shown here, by way of example, comprises an inner cylinder 24 and an outer cylinder 25, having, respectively smaller and greater diameters than the diameter of the annular cathode 15. Cylinders 2d and 25 have attached to each end thereof disk-like members 26, the disk-like members of inner cylinder 24 extending toward the disk-like members of cylinder 25 such that the space therebetween becomes a small annular slit at each end of the annular space formed by inner and outer cylinders 24 and 25, respectively, Cylinders 24 and 25 are spaced from disk 19 by circular spacers 27 and 23, respectively, adjacent the inner and outer edges of rods 27a. In order to more rigidly support the outer cylinder 25 and its end members 26, a plurality of ceramic rods 27a is embedded in disk 14 being attached thereto, for example, by cement. Rods 27a are positioned at the outer edge of disk 14 and extend for the length of the gun 12 parallel to the axis thereof passing through holes in disk 19 and the end disks 26 attached to cylinder 25. Rods 27a are rigidly attached to each of the elements they engage, for example, by cement.

Positioned on the opposite side of the focusing structure 23 from the disk 19 is an accelerating electrode comprising inner and outer disk members 3Q and 31, respectively. Inner disk 30 is insulated from the end disk 26 of inner focusing cylinder 24 by a ceramic spacing cylinder 32, and outer disk 31 is spaced from the end disk 26 of outer cylinder 25 by a ceramic spacing cylinder 33. An additional accelerating electrode is positioned on the opposite side of the aforementioned accelerating electrode, and comprises disks 34 and 35 which are, respectively, substantially similar to disks 30 and 31, and are spaced therefrom by ceramic spacing cylinders 36 and 37, respectively. As shown here, the slit apertures of the accelerating electrodes are of different size. However, any desired shape and configuration of accelerating electrode structure may be used.

Positioned on the opposite side of the accelerating electrodes from the focusing electrode structure is a set of deflection electrodes comprising inner and outer cylinders 3S and 39, respectively. Inner cylinder 3S is supported by end disks dil, one of end disks contacting a ceramic spacer 41 surrounding central ceramic cylinder 13 and contacting accelerating electrode 34. Outer deflection electrode 39 is supported by end disks 42 which are attached to ceramic rods 27a, one of disks 42 being spaced from outer electrode 35 by a ceramic cylinder 43. All the conductive electrodes of the focusing, accelerating and deflecting systems are suitably connected to separate lead -in-s whereby the `desired external electrical connection may be made.

The portion of the envelope 10 between the gun 12 and the fluorescent coating 11 may be coated, if desired with a conductive material Aquadag as shown, for example, at 4d, the purpose of which is to collect stray electrons. If desired, a positive potential may be applied to coating 44 by means of a lead-in connection, not shown, to further accelerate the electron stream. Surrounding the portion of the envelope 1t? between the electron gun 12 and the fluorescent coating 11 is a coil 45 which is fed from an alternating current source 46.

Application of the proper heater voltage, biasing voltage, focusing voltage and accelerating voltage to the proper electrodes will cause an electron beam to pass out through the gun and impinge on the coating 11 in circular form. The beam pattern will actually consist of' forty-eight separate beams, each controlled by one of the grids 17. By adjustment of the potential applied to the disk 19, the beams may be formed into spots on the coating 11. The size of the spots may be adjusted by adjusting this potential until with no defiection voltage applied to the deflection electrodes the spots will just overlap. When a potential is applied to the deiiection electrodes, the electrons will move away from the axis of the tube as they pass from the deiecting electrode structure toward the coating 11, and will be acted on by the alternating current field produced by coil d5.

Due to the component of motion in a radial direction, the magnetic field will excite a force on the electrons in a direction tangential to the circular pattern thereby producing elongation of the spot pattern on the coating 11. Since the amount of action of the magnetic field on the electrons is proportional to the density of the magnetic lield and the radial component of motion, deflecting the electrons to a larger extent to increase the size of the circular pattern will increase the length of the spots such that by proper adjustment of the amplitude of the alternating current source the spots may be made to touch, but not substantially overlap for all sizes of the circular pattern from zero deection to maximum deflection in a direction to increase the diameter of the circular pattern. The deiiection of the circle inward to decrease the diameter of the radial pattern would also cause elongation of the spots thereby producing an overlap. The alternating eld may be disconnected during those periods when it is desired to deflect the circular pattern inward to produce a smaller circle.

Referring now to FIG. 3, there is shown a modication of the device illustrated in FIGS. 1 and 2 wherein the electrostatic focusing has been replaced by magnetic focusing, ln this device, the envelope 1t), uorescent coating 11 and gun 12 are substantially similar to those shown in FG. l, except that the focusing and accelerating electrode structures comprising elements 19 through 37 have been removed. An accelerating structure comprises inner and outer cylinders E47 and i3 respectively, inner cylinder A17 being .supported by end disks 59 which engage support cylinder 13, and outer cylinder d3 being supported by end disks 5@ which engage rods 27a. Ceramic spacing cylinders 51 are provided 'between inner and outer end dis is 49 and 5@ and the cathode support disk 14, and ceramic spacing cylinders 52 are provided between the `other end disks attached to cylinders d'7 and and the deflection electrode end disks It@ and d2, respectively.

A focusing coil 53 is positioned around envelope 1t) coaxial therewith and adjacent the space between the accelerating electrodes comprising cylinders 47 and 48 and the deecting electrodes comprising cylinders 38 and 39. A coil 45 fed by alternating current source d6 similar to those shown in FIG. 1 may be provided, if desired, to produce elongation of the spots impinging on coating 11.

Electrons emanating from the surface of cathode 15, upon being passed by the gri-ds 17, and accelerated by the cylinders 47 and 48, will be influenced by a magnetic field which may be produced, for example, by passing a current through coil 53, for example, as shown here by means of a battery Se, such that electrons which are traveling parallel to the axis of the tube will encounter magnetic iux lines from coil 53 which are substantially parallel to their line of travel, and will be substantially unaffected thereby. However, electrons which are traveling in directions other than parallel to the axis of the tube will be caused to spiral as they travel toward the coating 11, and will cross the path of electrons traveling parallel to the axis of the tube once for every revolution of the spiral. Hence, by adjusting the intensity of the magnetic iield such that the electrons impinge on the coating 11 at a point Where the spiral electron trajectories intersect the straight-line trajectories, an image of the cathode 1S -will be formed by the pattern of the electrons on the coating. The electron trajectories will both be modiiied simultaneously by application of potentials to the deection electrodes, and hence any defocusing action produced by delection of the electron beams Will be small. lf desired, this defocusing may be compensated for by the simultaneous application of a potential change across the focusing coil 53.

Furthermore, if desired, any misfocusing produced by the magnetic field produced by coil 45 may be compensated for by application of a portion of lthe current from alternating current source 46 to the focusing coil 53.

This completes the description of the -specic embodiments of the invention illustrated herein. However, many modiiications thereof will be apparent to persons skilled in the art Without departing from the spirit and scope of this invention. For example, a combination of electrostatic and electromagnetic focusing could be used, and the particular positioning and structure of the elements of gun 12 are by Way of example only.

Furthermore, any number of grids 17 could be used, and said grids could take other forms. Accordingly, it is desired that this invention be not limited by the speciiic details of the embodiments described herein, except as dened by the appended claims.

What is claimed is:

1. An electron-discharge device comprising means for producing a plurality of electron-beam elements spaced along a curved path, `a plurality of grids, each grid being substantially insulated from and controlling one of said electron-beam elements substantially independently of the rest of said plurality of grids, and means for producing motion of said element along said path.

2. An electron-discharge device comprising means for producing a plurality of electron-beam element-s spaced along a circular path, a plurality of grids, each grid being substantially insulated from and controlling one of said electron-beam elements substantially independently of the rest of said plurality of grids, means acting on said element after the passage thereof through s aid grid for producing motion of said element along said path.

3. An electron-discharge device comprising means for producing a plurality of electron-beam elements spaced along a circular path, a plurality of grids, each grid controlling one of said electron-beam elements substantially independently of the rest of said plurality of grids, and means for producing motion of said elementalong said path comprising means for producing a magnetic field substantially axially of said circular path, and means for cyclically varying said magnetic field.

4. An electron-discharge device comprising means for producing a plurality of electron-beam elements spaced along a circular path, a plurality of grids, each grid controlling one of said electron-beam elements substantially independently of the rest of said plurality of grids, means for producing -motion of said element along said path comprising means for producing a magnetic iield substantially axially of said circular path, means for cyclically varying said magnetic field, and means for deecting said beam elements radially of said circular path.

5. An electron-discharge device comprising means for producing a plurality of electron-beam elements spaced along a circular path, a plurality of grids, each grid controlling one of said electron-beam elements substantially independently of the rest of said plurality of gr-ids, means for producing motion of said element along said path comprising means for producing a magnetic field Substantially axially of said circular path, and means for electrostatically deiiecting said beam elements radially of said circular path.

6. An electron-discharge device comprising an electronemitting surface lying along a curved path, a plurality of grids, each grid controlling electrons from na portion of said path substantially independently of the rest of said plurality of grids, a target, means for accelerating said electrons to said target, and means for focusing said electrons at said target comprising means for producing a magnetic eld substantially parallel to the desired average electron path between said electron-emitting surface and said target.

'7. An electron-discharge device comprising an electroneniitting surface lying along a circular path, and a plurality of grids, each grid controlling electrons from a portion of said path substantially independently of the rest of said plurality of grids, a target, means lfor accelerating said electrons to said target comprising means for producing a cyclically varying magnetic field substantially axially of said circular path.

3. An electron-discharge device comprising an electron-emitting surface lying along a circular path, a plurality of grids, each grid controlling electrons from a portion of said path substantially independently of the rest of said plurality of grids, a target, means for accelerating said electrons to said target, means for focusing said electrons at said target comprising means for producing a magnetic field substantially parallel to the desired average electron path between said electron-emitting surface and said target, and means for producing motion of the accelerated electrons along said path comprising means for producing a cyclically varying magnetic iield substantially axially of said circular path.

9. An electron discharge system comprising an electron tube having an electron source and a target electrode, means for forming electrons from said source into a plurality of electron beam elements, means for simultaneously directing said plurality of electron beam elements toward said target and controlling each of said electron beam elements independently of another of said electron beam elements, means for focusing said plurality of electron beam elements on said target, and means for cyclically varying said focusing means to cause a portion of said beam elements to move in a spiral motion toward said target.

10. Ari electron discharge system comprising an electron tube having an electron source and a target electrode, means for forming electrons from said source into the beam elements, means for simultaneously directing said plurality of electron beam elements toward said target means for controlling each of said electron beam elements substantially independently of the rest of said electron beam elements, means for focusing said plurality of electron beam elements on said target comprising a magnetic iield oriented substantially parallel to said beam, and means for cyclically Varying the intensity of said magnetic iield to cause a portion of said beam elements to move along a circumferential path toward said target.

11. An electron discharge device comprising, a single source of electrons, means for producing a plurality of electron-beam elements from said single source of electrons, a plurality of control elements, each control element being substantially insulated from and controlling one of said electron-beam elements substantially independently ofthe rest of said plurality of control elements, and means for producing motion of said elements along said paths.

References Cited by the Examiner UNITED STATES PATENTS 2,218,725 10/40 Schroeder 1 S16-Q31 X 2,707,758 5/55 Wang 315-35 GEORGE N. WESTBY, Primary Examiner.

RALPH G. NILSON, Examiner.

Claims (1)

1. AN ELECTRON-DISCHARGE DEVICE COMPRISING MEANS FOR PRODUCING A PLURALITY OF ELECTRON-BEAM ELEMENTS SPACED ALONG A CURVED PATH, A PLURALITY OF GRIDS, EACH GRID BEING SUBSTANTIALLY INSULATED FROM AND CONTROLLING ONE OF SAID ELECTRON-BEAM ELEMENTS SUBSTANTIALLY INDEPENDENTLY OF THE REST OF SAID PLURALITY OF GRIDS, AND MEANS FOR PRODUCING MOTION OF SAID ELEMENT ALONG SAID PATH.

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