EP0192336A1 - Focalisation d'un faisceau électronique dans un tube à rayons cathodiques - Google Patents

Focalisation d'un faisceau électronique dans un tube à rayons cathodiques Download PDF

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Publication number
EP0192336A1
EP0192336A1 EP86300411A EP86300411A EP0192336A1 EP 0192336 A1 EP0192336 A1 EP 0192336A1 EP 86300411 A EP86300411 A EP 86300411A EP 86300411 A EP86300411 A EP 86300411A EP 0192336 A1 EP0192336 A1 EP 0192336A1
Authority
EP
European Patent Office
Prior art keywords
cathode
screen
ray tube
loop
perimeter
Prior art date
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.)
Withdrawn
Application number
EP86300411A
Other languages
German (de)
English (en)
Inventor
Kern Ko Nan Chang
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.)
RCA Corp
Original Assignee
RCA Corp
Priority date (The priority date 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 date listed.)
Filing date
Publication date
Application filed by RCA Corp filed Critical RCA Corp
Publication of EP0192336A1 publication Critical patent/EP0192336A1/fr
Withdrawn legal-status Critical Current

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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
    • H01J29/56—Arrangements for controlling cross-section of ray or beam; Arrangements for correcting aberration of beam, e.g. due to lenses
    • H01J29/563—Arrangements for controlling cross-section of ray or beam; Arrangements for correcting aberration of beam, e.g. due to lenses for controlling cross-section
    • 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
    • H01J29/80—Arrangements for controlling the ray or beam after passing the main deflection system, e.g. for post-acceleration or post-concentration, for colour switching

Definitions

  • This invention relates to a cathode ray tube and is concerned with focusing means for altering the trajectory of an electron beam within the tube.
  • a standard cathode-ray tube comprises a faceplate panel with a cathodoluminescent screen, a funnel-shaped back section having a protruding neck, and a mount containing an electron gun adapted to emit a beam of electrons for striking the screen.
  • a deflection yoke alters the trajectory of the electron beam so that it scans the entire cathodoluminescent screen.
  • the maximum angle that the beam is deflected to diagonal corners of the tube screen is known as the deflection angle.
  • Typical values for the deflection angle are 70°, 90° and 110°, which represent the total corner-to-opposite corner angle through which the electron beam is deflected. For example, a deflection angle of 110° means that the electron beam is deflected 55° from center to corner.
  • a cathode-ray tube having a faceplate panel and an electron gun adapted to emit a beam of electrons for striking a cathodoluminescent screen disposed on said panel, characterized by conductive focusing means disposed around the perimeter of said screen and insulated therefrom, for locally altering the trajectory of said electron beam adjacent said perimeter.
  • a method of focusing a beam of electrons emanating from an electron gun of a cathode-ray tube and striking a cathodoluminescent screen disposed on a faceplate panel of said tube characterized by the step of applying a significantly lower voltage to a conductive loop disposed around the perimeter of said screen than to said screen, in order to locally alter the trajectory of the electron beam adjacent said perimeter.
  • a cathode-ray tube employs localized focusing means whereby the trajectory of a beam of electrons, emanating from an electron gun of the tube and striking a cathodoluminescent screen, is locally altered adjacent the perimeter of the screen.
  • Conductive focusing means is disposed around the perimeter of the screen for altering the electron beam trajectory, and has a significantly different voltage applied thereto than to the screen.
  • a preferred embodiment of the present invention provides a localized retarding field in the vicinity of large deflection in order to achieve a more favorable landing angle of the electron beam on the cathodoluminescent screen.
  • the electron gun 14 is part of a mount 18 which is frit sealed to a back section 20 of the tube 10 .
  • the back section 20 is substantially symmetrical in shape to that of the faceplate panel 12 in order to form a thin cathode-ray tube 10.
  • Such a thin tube 10 has a large deflection angle which may be as high as 150°.
  • An apertured shadow mask 22 is positioned near the screen 16 and attached to a mask frame 24, which is supported by mounting studs 26 that extend inwardly from the faceplate panel 12.
  • Conductive focusing means is disposed around the perimeter of the cathodoluminescent screen 16 and insulated therefrom.
  • the conductive focusing means comprises a metallic loop 28 which is mounted near the edge of and in back of the shadow mask 22.
  • the loop 28 is attached to insulating posts 30 by screws.
  • the insulating posts 30 may be made of a ceramic material, and are attached to the shadow-mask frame 24 by partially-imbedded bolts (not shown).
  • the posts 30 have a cylindrical-shaped outer surface 32 with a plurality of spaced circular grooves 34 adjacent thereto, as illustrated in FIGURE 3.
  • the purpose of the grooves 34 is to prevent getter material, deposited thereon when a getter 36 within the tube 10 is subsequently flashed, from creating a conductive path between the metallic loop 28 and the screen 16 which is at a voltage significantly different from that of the loop 28.
  • the metallic loop 28 comprises a rectangular-shaped band having a width of about 12 millimeters and a thickness of about 1 millimeter.
  • the band should be attached to the insulating posts 30 in a manner wherein the major surface area of the band is positioned in a plane substantially parallel to the trajectory of the electron beams, for reasons explained further below.
  • the loop 28 may alternatively comprise a circular wire having a diameter of about 1.5 millimeters.
  • the metallic loop 28 is made of either nonmagnetic stainless steel or a nonmagnetic alloy of nickel and chromium. In order to be able to apply a voltage to the loop 28, a conductive lead 38 is welded to the loop 28 and passes through apertures in both the frame 24 and the faceplate panel 12.
  • the lead 38 should be made of an alloy compatible with the glass material of the panel 12.
  • the portion of the lead 38 adjacent the inside surface of the faceplate panel 12 is surrounded by an insulating tube 40 in order to prevent getter material from creating a conductive path between the lead 38 and the anode (not shown) which is at a significantly higher voltage.
  • a lower voltage is applied to the conductive loop 28 than to the cathodoluminescent screen 16 or anode.
  • the voltage difference is about 15kV.
  • the voltage applied to the loop 28 is about 10kV, while the voltage on the screen is about 25kV. This voltage difference creates a localized retarding field in the vicinity of large deflection which occurs adjacent the perimeter of the screen 16.
  • FIGURE 4 The significance of this retarding field is shown diagrammatically in FIGURE 4.
  • an electron beam 42 approaches the cathodoluminescent screen 16 in the vicinity of the conductive loop 28, the beam 42 is bent away from the loop 28 and toward the screen 16, causing a smaller angle of incidence for the electron beam trajectory adjacent the screen 16.
  • This more favorable landing angle for the electron beam 42 results in a better cathodoluminescent spot size adjacent the perimeter of the screen 16, i.e., one that is smaller in diameter and, thus, better focused. In other words, a better spot size is obtained at large deflection angles because of the retarding field.
  • the diameter of a spot luminesced by unretarded electron beams is larger than the diameter of the spot luminesced by retarded electron beams, labeled as B.
  • the ultor or screen voltage was about 25kV and the voltage applied to the conductive loop 28 was about lOkV
  • spot size can be reduced from 2mm in diameter to about 1.3mm by using the conductive loop 28, which represents a reduction in spot size of approximately 35%.
  • a 150° angle of deflection which has not been previously feasible, is within reach with good spot sizes across the entire display area.
  • This realization of a more favorable landing angle for the electron beam 42 on the cathodoluminescent screen 16, in the vicinity of large deflection, has significant application in the fabrication of a thin cathode-ray tube 10 where the spacing between the electron gun 14 and the screen 16 is limited.
  • the focusing loop 28 enables a tube 10 with a deflection angle larger than 110° to achieve good image size and increased transmission current (brightness) at the perimeter of the screen 16, due to the larger angle of incidence for the electron beam 42 caused by the local retarding field.
  • the retarding field and resulting focusing effect are able to be applied to a plurality of beam trajectories which strike the screen 16 at distances further away from the perimeter thereof, thereby achieving the desirable focusing benefits over a greater area of the screen 16 adjacent the perimeter.
  • the present invention may also be utilized in cathode-ray tubes having deflection angles of 110° or less in order to further improve their performance by enhancing picture resolution and brightness at the corners of the screen.

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  • Cathode-Ray Tubes And Fluorescent Screens For Display (AREA)
EP86300411A 1985-01-29 1986-01-21 Focalisation d'un faisceau électronique dans un tube à rayons cathodiques Withdrawn EP0192336A1 (fr)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
US69588485A 1985-01-29 1985-01-29
US695884 1985-01-29

Publications (1)

Publication Number Publication Date
EP0192336A1 true EP0192336A1 (fr) 1986-08-27

Family

ID=24794832

Family Applications (1)

Application Number Title Priority Date Filing Date
EP86300411A Withdrawn EP0192336A1 (fr) 1985-01-29 1986-01-21 Focalisation d'un faisceau électronique dans un tube à rayons cathodiques

Country Status (3)

Country Link
EP (1) EP0192336A1 (fr)
JP (1) JPS61176038A (fr)
DD (1) DD241667A5 (fr)

Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4160187A (en) * 1975-11-05 1979-07-03 Gte Sylvania Incorporated Post-deflection acceleration crt system
US4331903A (en) * 1978-11-21 1982-05-25 Tokyo Shibaura Denki Kabushiki Kaisha Color picture tube and method for magnetically adjusting the color picture tube

Patent Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4160187A (en) * 1975-11-05 1979-07-03 Gte Sylvania Incorporated Post-deflection acceleration crt system
US4331903A (en) * 1978-11-21 1982-05-25 Tokyo Shibaura Denki Kabushiki Kaisha Color picture tube and method for magnetically adjusting the color picture tube

Non-Patent Citations (1)

* Cited by examiner, † Cited by third party
Title
PATENT ABSTRACTS OF JAPAN, unexamined applications, E section, vol. 6, no. 182, September 18, 1982 THE PATENT OFFICE JAPANESE GOVERNMENT page 74 E 131 *

Also Published As

Publication number Publication date
DD241667A5 (de) 1986-12-17
JPS61176038A (ja) 1986-08-07

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Inventor name: CHANG, KERN KO NAN