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US2524606A - Electron discharge device - Google Patents

Electron discharge device Download PDF

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Publication number
US2524606A
US2524606A US5847A US584748A US2524606A US 2524606 A US2524606 A US 2524606A US 5847 A US5847 A US 5847A US 584748 A US584748 A US 584748A US 2524606 A US2524606 A US 2524606A
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United States
Prior art keywords
plates
deflection
plate
potential
screen
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Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Expired - Lifetime
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US5847A
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English (en)
Inventor
Shelton Edward Eric
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
AC Cossor Ltd
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AC Cossor Ltd
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Filing date
Publication date
Application filed by AC Cossor Ltd filed Critical AC Cossor Ltd
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Classifications

    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
    • H01J29/00—Details of cathode-ray tubes or of electron-beam tubes of the types covered by group H01J31/00
    • H01J29/46—Arrangements of electrodes and associated parts for generating or controlling the ray or beam, e.g. electron-optical arrangement
    • H01J29/70—Arrangements for deflecting ray or beam
    • H01J29/72—Arrangements for deflecting ray or beam along one straight line or along two perpendicular straight lines
    • H01J29/74—Deflecting by electric fields only

Definitions

  • This invention relates tocathode ray tubes -of the kind in which the beam is deflected successively in two mutually perpendicular directions, and in which at least the second of these deflections (herein called the X deflection) is produced electrostatically. In such cases it is customary, although not essential, for the firstdeflection (herein called the Y deflection) also to be produced electrostatically.
  • the principal object of the invention is to avoid deflection amplitude distortions (namely, trapezium, pin-cushion and barrel distortions) of the raster when the deflection voltages are ap plied asymmetrically and when large angles of ⁇ deliection are produced.
  • a double electrostatic deflection cathode ray tube having an interplate screen and wherein both of the X deiiection plates have their entrance and emergent edges curved concavely, and have at least part of their surfaces curved conveidy toward each other so thattheir central parts are closer together than their sides, whereby deflection amplitude distortions are substantially eliminated when the tube is operated with total angles of deiiection up to at least about thirty degrees, even though the potentials of one X deection plate-andlone Y deflection plate be held constant and the deflection voltages be applied wholly to the other deflection plates.
  • interplate screenl in this speci-Av v cation is meant an electrode placed across the path of the beam, between the region ofYdeectio-n and the region of X deflection, curved spherically about substantially the apparent ⁇ cen-- tre of Y deflection, ⁇ or-cylindrically about an axis passing substantially through that centre and perpendicular to the plan-e of Y deflection, and slotted so as to allow passage of the beam at all required angles of:Y deflection.
  • This inter plate screen is maintained at constant pctential when the tube is in operation, usually the ⁇ potential of the nal anode of the electron gun.
  • the effect of the interplate screen is presumed to be the shaping of the equifpotential-lines of ⁇ the eld between theentrance'edges of the plates so that they are crossed substantially atcright angles by the beam under all degrees of Y deflection. This prevents the refraction ofthe elec- 7 claims. (c1. 25o-15s) tron beam towards the axis when entering the space between the X plates and trapezium distortion due to this cause is, therefore, eliminated.
  • the curvature of the entrance edges of the X" plates is for the same purpose.
  • the emergent edges of the plates are curved concavely for the similar .purpose of preventing or compensating for refraction of the beam in the direction of Y deection when emerging from the space between the X plates.
  • each plate in its middle is considerably less than its length at its sides.
  • Compensation for the resulting variation with Y deflection of X deflection sensitivity is effected by the curving of at least part of the surfaces of the X plates convexly toward each other so that their central parts are closer together thanvtheir sides.
  • an additional electrode is provided beyond each X deflection plate, or at least beyond the working X plate (i. e. that X deection plate which is arranged for its potential to be varied during operation while the potential of the other is kept constant) said additional electrode being situated outside the extreme deflected path of the beam and being arranged to be operated at a constant potential, whereby the collection by the said X plate of secondary electrons returning from the screen is substantially prevented.
  • a further effect of this additional electrode is to reduce the defocussing of the beam which tends to occur when the beam is deflected to pass close to the working X plate.
  • the conductiveA coating on the wall of the envelope, or the shield surrounding the deflector plates, iprovided for the purpose of collecting secondary electrons returning from the screen is preferably maintained at the same constant'potential as this additional electrode, which may be the highest potential attained by the working X plate during operation.
  • Fig. 1 is an elevational view of the deflecting electrode construction of a cathode ray tube embodying the principles of the present invention
  • Fig. 2 is a horizontal sectional View of the electrode structure shown in Fig. 1J taken along the linelZ--Z of Fig. l,
  • Fig. 3 is an exploded view in perspective of one pair of deflection plates of the deilecting structure shown in Figs. 1 and 2, while Fig. 4 is a diagrammatic representation of a cathode ray tube embodying the principles of the present invention in which there is generally indicated the arrangement of the various electrodes within the tube and the potentials applied thereto.
  • reference character I indicates the final anode of an electron gun which projects an electron beam generated at a cathode (not sho-wn) along the axis of the electrode structure.
  • the beam after passing through the central aperture 2 inanode I, passes between the Y deiiecting plates 3 and 4 and through the slot 5a in interplate screen 5. Its path continues between the X deflecting plates 6 and 1 and between the secondary electron collector electrodes 8 and 9 and is directed toward a screen at the end of envelope 30 (Fig. 4). It will be noted that each of the Y deflecting plates 3 and 4 are so bent intermediate their ends so as to form a gradually increasing space between them toward the exit.
  • Inter-plate screen 5 is an electrode placed across the path of the beam and curved symmetrically about an axis passing substantially through the apparent center of Y deflection and slotted so as to allow passage of the beam through aperture 5a at all required angles of Y deection.
  • the interplate screen 5 is maintained at a constant potential when the tube is in operation, usually that of the final anode of the electron gun'.
  • the effect of the inter-plate screen 5 is presumed to be a shaping of the equi-potential lines of the eld between the entrance edges of the X plates 6 and 1, so that they are crossed substantially at right angles by the beam under all degrees of Y deflection. This prevents the refraction of the electron beam towards the axis when entering the space between the X plates 6 and 1. Trapezium distortion due to this cause is therefore eliminated.
  • the final deflection plates 6 and 1 are identical with each other.
  • each of the plates 6 and 1 is made up of two plane sections I1 and I8 and a curved middle section I9. Plane sections I1 are parallel one to the other while the curved sections and exit sections I8 form a divergent anglealong the undeflected path of the beam.
  • the curvature of the middle section I9 is such that all sections thereof cut by planes parallel to the plane of Fig. 2 are rectilinear.
  • the curvature is convex inwardly so that the central part I9 of plate 6 is closer to the central part I9 lof plate 1, than are the upper and lower edge portions of plate 6, where lips are provided, with regard to the corresponding sides of plate 1.
  • Plates 6 and 1 are reinforced by the turned-over lip portions 20 at their upper and lower edges.
  • Fig. 4 is shown a schematic representation of a cathode ray tube having an evacuated envelope 30 having a funnel-shaped conguration.
  • the fluorescent screen (not shown) occupies the large end wall of the envelope while the electron gun structure and deflecting electrode system occupies the neck of the envelope.
  • One of the Y deflecting plates 3 may have a saw tooth deflecting wave of low frequency applied to it as indicated by the saw tooth figure at the end of the connection lead connected to plate 3, while the other, 4, is held at a constant positive potential as indicated by the -I mark.
  • the interplate screen 5 may be directly connected to plate 4 or it may be separately energized from ⁇ a fixed potential power equal to that of plate c as indicated in the figure.
  • plate 1 is held at a fixed potential while plate 6 has a high fref quency saw tooth wave applied thereto.
  • the envelope 30 of the cathode ray tube is preferably provided with a conductive coating 3! on the inside of the envelope which is maintained at the same potential and may be directly connected to the additional electrodes 8 and 9 as indicated in Fig. 4.
  • the tube illustrated in the drawing is entirely symmetrical, and an additional electrode 8 or 9 is provided for each X deflecting plate 6 or 1. It is, therefore, immaterial which of the X plates 6 and 1 is held at fixed potential, and which is used as the working plate in Fig. 4. Merely for the sake of illustration, plate 1 is indicated as being held at a xed potential.
  • the present invention will principally be applied to cathode ray tubes having fluorescent screens, but it is evident that the precise nature of the screen is irrelevant to the invention, and the invention may be used in all cases where asymmetric distortion voltages are employed, and wide angles of deflection are required. Also, the invention is applicable to cathode ray tubes of the gas lled type, as well as to those in which the focusing of the beam is mainly affected by electro-static elds. As, however, the beam current of gas lled tubes is not modulated during operation, the secondary electron collecter electrodes 8 and 9 do not serve the same total purpose, though they still act to increase the apparent plate to plate impedance presented to the driving circuit.
  • a cathode ray tube according to claim 1, wherein an additional electrode is provided beyond that X deflection plate which is arranged for its potential to be varied during operation, said additional electrode being arranged outside the extreme deflected path of the beam and being arranged to be operated at a constant potential whereby the collection by the said X plate of secondary electrons returning from the screen is substantially prevented.
  • a cathode ray tube according to claim 1, wherein said X-plates are symmetrically constructed for operation with either of the X deflection plates held at constant potential and with the deflection voltages applied to the other of such X deflection plates, and including an additional electrode is provided beyond the X deflection plate which is arranged to receive a variable potential during operation, said additional electrode being arranged outside the eXtreme deflected path of the electron beam and being arranged to be operated at a constant potential whereby the collection by the said X plate of secondary electrons returning from the screen is substantially prevented.
  • a cathode ray tube wherein the potential of one of said X deection platesis held constant and the other of said X deflection plates has deflection voltages applied thereto and wherein an additional electrode is provided beyond the latter of said X deflection plates, said additional electrode being operated at a constant potential whereby the collection of secondary electrons by said latter plate is substantially prevented.
  • a cathode ray tube having within an evacuated envelope a source for a beam of electrons, a first pair of opposing deilection plates and a second pair of opposing deflection plates arranged in planes perpendicular to said rst pair of plates, said second pair of plates havingentrance and emergent edges curved concavely and at least part of their facing surfaces curved convexly toward each other, so that their central parts are closer together than the side parts whereby deflection amplitude distortions are substantially eliminated, the potential of one of said rst pair of deflection plates and one of said second pair of deflection plates being held constant and the other of each of said pairs of plates having deilection voltages applied thereto.
  • a cathode ray tube according to claim 6, wherein an additional electrode is provided beyond that one of said second pair of deflection plates which is arranged for its potential to be varied during operation and outside the path of said beam when grazing the said one of said second pair of deflection plates, said additional electrode being operated at a constant potential whereby the collection by said plate of secondary electrons is substantially prevented.

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  • Vessels, Lead-In Wires, Accessory Apparatuses For Cathode-Ray Tubes (AREA)
  • Cathode-Ray Tubes And Fluorescent Screens For Display (AREA)
US5847A 1939-05-26 1948-02-02 Electron discharge device Expired - Lifetime US2524606A (en)

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
GB15769/39A GB529523A (en) 1939-05-26 1939-05-26 Improvements in electron discharge devices

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US2524606A true US2524606A (en) 1950-10-03

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US5847A Expired - Lifetime US2524606A (en) 1939-05-26 1948-02-02 Electron discharge device

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US (1) US2524606A (it)
BE (1) BE481370A (it)
GB (1) GB529523A (it)

Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2633553A (en) * 1948-11-26 1953-03-31 Siemens Ag Cathode-ray oscillograph
US2833947A (en) * 1952-10-28 1958-05-06 Telefunken Gmbh Electron beam deflecting system
US2834902A (en) * 1953-07-18 1958-05-13 Telefunken Gmbh Deflection system for cathode ray tubes
US3151270A (en) * 1961-03-31 1964-09-29 Bell Telephone Labor Inc Electron ribbon beam encoder tube with beam tilt control

Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2212396A (en) * 1936-07-31 1940-08-20 Gen Electric Cathode ray tube
US2228958A (en) * 1938-11-23 1941-01-14 Fides Gmbh Cathode ray tube
US2266621A (en) * 1940-08-23 1941-12-16 Rca Corp Cathode ray tube system

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2212396A (en) * 1936-07-31 1940-08-20 Gen Electric Cathode ray tube
US2228958A (en) * 1938-11-23 1941-01-14 Fides Gmbh Cathode ray tube
US2266621A (en) * 1940-08-23 1941-12-16 Rca Corp Cathode ray tube system

Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2633553A (en) * 1948-11-26 1953-03-31 Siemens Ag Cathode-ray oscillograph
US2833947A (en) * 1952-10-28 1958-05-06 Telefunken Gmbh Electron beam deflecting system
US2834902A (en) * 1953-07-18 1958-05-13 Telefunken Gmbh Deflection system for cathode ray tubes
US3151270A (en) * 1961-03-31 1964-09-29 Bell Telephone Labor Inc Electron ribbon beam encoder tube with beam tilt control

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Publication number Publication date
GB529523A (en) 1940-11-22
BE481370A (it)

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