EP0589522B1 - Kathodenstrahlröhre - Google Patents

Kathodenstrahlröhre Download PDF

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Publication number
EP0589522B1
EP0589522B1 EP19930202690 EP93202690A EP0589522B1 EP 0589522 B1 EP0589522 B1 EP 0589522B1 EP 19930202690 EP19930202690 EP 19930202690 EP 93202690 A EP93202690 A EP 93202690A EP 0589522 B1 EP0589522 B1 EP 0589522B1
Authority
EP
European Patent Office
Prior art keywords
electrode
control electrode
ray tube
cathode
aperture
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.)
Expired - Lifetime
Application number
EP19930202690
Other languages
English (en)
French (fr)
Other versions
EP0589522A1 (de
Inventor
Jeroen Van Engelshoven
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.)
Koninklijke Philips NV
Original Assignee
Koninklijke Philips Electronics NV
Philips Electronics NV
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 Koninklijke Philips Electronics NV, Philips Electronics NV filed Critical Koninklijke Philips Electronics NV
Priority to EP19930202690 priority Critical patent/EP0589522B1/de
Publication of EP0589522A1 publication Critical patent/EP0589522A1/de
Application granted granted Critical
Publication of EP0589522B1 publication Critical patent/EP0589522B1/de
Anticipated expiration legal-status Critical
Expired - Lifetime legal-status Critical Current

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    • 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
    • H01J29/48—Electron guns
    • H01J29/488—Schematic arrangements of the electrodes for beam forming; Place and form of the elecrodes
    • 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

Definitions

  • the invention relates to a cathode ray tube device comprising a cathode ray tube comprising in an evacuated envelope means to generate at least one electron beam behind which means, viewed in the direction of propagation of the electron beam, are provided successively a control electrode, an accelerating pre-focusing lens comprising a first and second lens electrode, each of said electrodes having an aperture for passing the at least one electron beam, and a main focusing lens, the device further comprising means to supply electric voltages to the electrodes, the cathode ray tube further comprising a phosphor screen on the inside of the evacuated envelope.
  • Such devices are known and used for instance for displaying monochromatic or multicolour pictures, for example television pictures.
  • Spot sizes meaning the average size of the spot at the centre of the phosphor screen within which 95% of all electrons of the beam hit the screen, of less than approximately 0.75 mm are attainable with known devices.
  • Increasing the beam current has an advantage because it increases the brightness of the spot.
  • An increased brightness of the spot is advantageous because e.g. an increase of contrast of the displayed images can be obtained, or a darker glass can be used for the envelope, which improves the image quality.
  • the spot size is increased, which decreases the image quality.
  • the beneficial effects of an increased beam current are negated by the negative effect of the increased spot size. It is an object of the present invention to achieve an improvement of the image quality.
  • a display device is characterized in that the means to supply voltages to the electrodes comprise means to supply a voltage difference V G2 between the control electrode and the first lens electrode, V 12 , being greater than 800 Volt, and in that V G2 /S 12 is greater than 4 Kev/mm, S 12 being the distance between the control electrode and the first electrode and in that in operation the beam current is limited to an upper limit of 1 mA.
  • the following effect occurs due to the electrical field between the control electrode and the first electrode.
  • the outermost rays of an electron beam emitted by the means for generating an electron beam are more focused than the paraxial rays by the electrical fields between the control electrode and the first lens electrode.
  • a cross-over is thereby formed.
  • the invention is a.o. based on the insight that for beam currents of the order of 0.5 to 1 mA the crossover occurs at a potential approximately around 800 V, and that the crossover location in space is a.o. dependant on the voltage difference V G2 between the control electrode and the first lens electrode.
  • the voltage difference between the control electrode and the first lens electrode in current designs of low-current cathode ray tubes is approximately 500 V, and the field strength E 12 between the control electrode and the first electrode is approximately 2.5 keV/mm.
  • Such a voltage difference between the control electrode and the first lens electrode combined with such a field strength results in a crossover location approximately at a position underneath the first lens electrode.
  • a voltage difference of more than 800 kV and a field strength between the control electrode and the first electrode of more than 4 kV/mm leads to a crossover at a position in between the control electrode and the first electrode.
  • the spot size is achieved, in particular for electron beams having a beam current of approximately 0.8 mA a spot size of less than 0.75 mm is obtained.
  • the beam current has been increased relative to the known devices, whereas the spot size has not been increased, resulting in an improved image quality.
  • the field strength is larger than 6 kV/mm and smaller than 9 kV/mm.
  • a preferred embodiment is characterized in that the aperture size of the aperture in the control electrode is less than approximately 500 ⁇ m.
  • a further preferred embodiment is characterized in that the aperture size of the aperture in the control electrode is larger than approximately 150 ⁇ m.
  • the aperture size becomes less than 150 ⁇ m than either the distance between the control electrode and the means for generating the electron beam and/or the thickness of the control electrode have, in order to obtain a beam current of 0.8 mA, to be reduced to such small values that either there is a great risk of incidental electrical contact between the control electrode and the means for generating the electron beams or the mechanical strength of the control electrode is inferior.
  • aperture size (d) is meant the size of the aperture, i.e. the square root of the area (A) of the aperture divided by ⁇ /4.
  • aperture ⁇ (4 A / ⁇ ) size equals the diameter.
  • Figure 1 is a horizontal longitudinal sectional view through a cathode-ray tube for use in a display device according to the invention.
  • Figure 2 is a longitudinal sectional view through an electron gun as used in the display device shown in figure 1.
  • Figure 3 shows a close-up detail of the electron gun shown in figure 2.
  • Figure 4 shows in a graphical form the spot size as a function of voltage.
  • Figure 5 shows in a graphical the spot size as a function of field strength.
  • FIG. 1 is a horizontal longitudinal sectional view of a cathode ray tube for a device according to the invention.
  • the cathode ray tube is a colour cathode ray tube for use in a device for displaying colour pictures.
  • an electron gun system 5 which generates three electron beams 6, 7 and 8 which, in this example, are situated with their axes in one plane (for example the plane of drawing).
  • the axis of the central electron beam 7 approximately coincides, when undeflected, with the tube axis.
  • the display window 2 comprises on its inside surface 9 a display screen 10 which display screen comprises, for example, a great number of triplet phosphor lines.
  • Each triplet comprises a line consisting of a blue-luminescing phosphor, a line consisting of a red-luminescing phosphor, and a line consisting of a green-luminescing phosphor.
  • the phosphor lines are, for example, substantially perpendicular to the plane of drawing.
  • a shadow mask 11 Positioned in front of the display screen 10 is a shadow mask 11 in which a large number of apertures 12 is provided through which the electron beams 6, 7 and 8 pass which each impinge only upon phosphor lines of one colour.
  • the three electron beams situated in one plane are deflected by the system of deflection coils 13.
  • the invention is not restricted to the type of device shown, it may for instance be used in a device having a mono-chromatic cathode ray tube or a camera tube.
  • the device further comprises means for supplying electric voltages to the electrodes. In figure 1 these means are schematically indicated by means 14.
  • Figure 2 is a longitudinal sectional view through an electron gun 21 as used in the examplary display device shown in figure 1.
  • the electron gun 21 comprises a means for generating at least one electron beam. In this example it comprises three cathodes 22, 23 and 24 for generating three electron beams 6, 7 and 8.
  • the electron gun further comprises a control electrode 25 which in this example is a joint electrode for the three electron beams. It further comprises a first lens electrode 26 and a second lens electrode 27. The first and second electrode 26, 27 form a pre-focusing lens.
  • the electron gun further comprises an electrode 28.
  • the electrodes 27 and 28 form a main lens. Each electrode has apertures for passing the electron beams.
  • the control electrode 25 is customarily called the G 1 -electrode
  • the first lens electrode is customarily called the G 2 -electrode.
  • Figure 3 shows schematically a close-up detail of the electron gun shown in figure 2.
  • the potential of the equipotential lines is indicated.
  • the diameter of the aperture in electrode 25 is indicated.
  • the size D of the aperture in control electrode in this example is approximately 250 ⁇ m.
  • the size of the aperture is to be understood to mean the average size of the aperture defined by the square root of the area of the aperture divided by ⁇ /4. For a circular aperture the size of the aperture is equal to the diameter. However, the invention is not restricted to circular apertures.
  • the aperture in control electrode 25 can be for instance oval or rectangular.
  • FIG 3 the trajectories of electrons 31 emitted by the emitting surface of cathode 22 are shown for a beam current of 0.8 mA. It is shown in figure 3 that the outermost electrons cross each other before paraxial electron, i.e. electrons that are emitted near the centre of the cathode, cross each other. A so-called cross-over point is formed approximately at point 29. This point lies slightly below the 800 Volt equipotential line.
  • the potential difference between control electrode 25 and first lens electrode 26 is greater than 800 V, in this example approximately 1200 Volt.
  • the crossover occurs at a potential approximately around 800 V, and that the crossover location in space is a.o. dependant on the voltage difference between the control electrode and the first lens electrode.
  • the voltage on the first lens electrode in known devices is typically approximately 500 Volt.
  • a voltage difference between the control electrode and the first lens electrode of this magnitude combined with a relatively low field strength (smaller than 4 kV/mm) results in a crossover location 29 approximately underneath the first electrode 26.
  • a voltage difference of more than 800 kV and a field strength between the control electrode and the first electrode of more than 4kV leads to a crossover in between the control electrode and the first electrode (see e.g. fig. 3).
  • an improvement of the spotsize is achieved.
  • Table 1 gun # #1 #2 #3 #4 G1 diameter[mm] .35 .25 .20 .15 E 12 [kV/mm] 2.8 7.7 6.8 6.1 V G2 [V] 552 1239 1231 601 0.8 mA 5% spot[mm] .90 .70 .68 .77
  • the last lines of table 1 gives the spotsize on the screen for an electron beam with a beam current of 0.8 mA.
  • the denotation 5% spot means that within the given diameter 95% of all electrons in the electron beam hit the screen. Below this will, for simplicity, also be called "the spot size".
  • Table 1 shows that making V G2 to be above 800 V and E 12 to be larger than 4 kV/mm reduces the spotsize.
  • Figure 4 shows the spotsize of a 0.8 mA electron beam for a fixed fieldstrength E 12 of 7.7 keV/mm as a function of the voltage difference V G2 .
  • Figure 5 shows, for a fixed voltage difference of V G2 of 1239 V, the spot size as a function of the field strength E 12 .
  • Crosses indicate that the diameter of the aperture in G1 is 250 ⁇ m, open squares indicate that said diameter is 200 ⁇ m, full squares that said diameter is 150 ⁇ m.
  • the field strength E 12 is larger than 6 keV/mm. Between 4 and 6 keV/mm the spot size decreases whereas above 6 keV/mm the decrease is less prominent. Preferably E 12 is less than 9 keV/mm. For values higher than 9 keV/mm the decrease in spot size is small, however, the change that arcing between electrodes G1 and G2 occurs is relatively high. Arcing may damage the electrodes.
  • the spot size is to a small degree dependent on the diameter of the aperture in electrode G1.
  • the aperture is smaller than 500 ⁇ m.
  • the diameter is larger than 150 ⁇ m. If the aperture size becomes less than 150 ⁇ m than either the distance between the control electrode and the means for generating the electron beam and/or the thickness of the control electrode have, in order to obtain reasonable beam currents, to be reduced to such small values that either there is a great risk of incidental electrical contact between the control electrode and the means for generating the electron beams or the mechanical strength of the control electrode is inferior.

Landscapes

  • Cathode-Ray Tubes And Fluorescent Screens For Display (AREA)

Claims (5)

  1. Elektronenstrahlröhrenanordnung mit einer Elektronenstrahlröhre, die in einer evakuierten Hülle (1) Mittel (21) aufweist zum Erzeugen wenigstens eines Elektronenstrahls, wobei hinter diesen Mitteln, gesehen in der Richtung der Fortpflanzung des Elektronenstrahls, hintereinander eine Steuerelektrode (25), eine beschleunigende Vorfokussierungslinse mit einer ersten (26) und einer zweiten (27) Linsenelektrode, wobei jede der genannten Elektroden eine Öffnung aufweist zum Hindurchlassen des wenigstens einen Elektronenstrahls, sowie eine Hauptfokussierungslinse (27, 28) vorgesehen sind, wobei die Anordnung weiterhin Mittel (14) aufweist zum Liefern elektrischer Spannungen zu den Elektroden, wobei die Elektronenstrahlröhre weiterhin auf der Innenseite der evakuierten Hülle einen Phosphorschirm (10) aufweist, dadurch gekennzeichnet, daß die Mittel (14) zum Liefern von Spannungen zu den Elektroden Mittel aufweisen zum Liefern einer Spannungsdifferenz VG2 zwischen der Steuerelektrode (25) und der ersten Linsenelektrode (26), wobei diese Differenz VG2 größer ist als 800 Volt, und daß VG2/S12 größer ist als 4 Kev/mm, wobei S12 der Abstand zwischen der Steuerelektrode (25) und der ersten Elektrode (26) ist und daß im Betrieb der Strahlstrom auf eine obere Grenze von 1 mA begrenzt ist.
  2. Elektronenstrahlröhrenanordnung nach Anspruch 1, dadurch gekennzeichnet, daß VG2/S12 größer ist als 6 keV/mm.
  3. Elektronenstrahlröhrenanordnung nach Anspruch 1 oder 2, dadurch gekennzeichnet, daß VG2/S12 kleiner ist als 9 keV/mm.
  4. Elektronenstrahlröhrenanordnung nach Anspruch 1, 2 oder 3, dadurch gekennzeichnet, daß die Öffnungsgröße der Steuerelektrode (25) kleiner ist als 0,5 mm.
  5. Elektronenstrahlröhrenanordnung nach Anspruch 1, 2, 3 oder 4, dadurch gekennzeichnet, daß die Öffnungsgröße der Steuerelektrode (25) größer ist als 0,15 mm.
EP19930202690 1992-09-25 1993-09-17 Kathodenstrahlröhre Expired - Lifetime EP0589522B1 (de)

Priority Applications (1)

Application Number Priority Date Filing Date Title
EP19930202690 EP0589522B1 (de) 1992-09-25 1993-09-17 Kathodenstrahlröhre

Applications Claiming Priority (3)

Application Number Priority Date Filing Date Title
EP92202947 1992-09-25
EP92202947 1992-09-25
EP19930202690 EP0589522B1 (de) 1992-09-25 1993-09-17 Kathodenstrahlröhre

Publications (2)

Publication Number Publication Date
EP0589522A1 EP0589522A1 (de) 1994-03-30
EP0589522B1 true EP0589522B1 (de) 1997-03-05

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Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US7113599B2 (en) 2000-09-08 2006-09-26 Symantec Corporation Location-independent packet routing and secure access in a short-range wireless networking environment
US7197308B2 (en) 2000-08-11 2007-03-27 Symantec Corporation Enabling seamless user mobility in a short-range wireless networking environment
US7224979B2 (en) 2001-05-03 2007-05-29 Symantec Corporation Location-aware service proxies in a short-range wireless environment

Family Cites Families (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
BE785749A (fr) * 1971-07-02 1973-01-02 Philips Nv Tube de camera de television (vidicon) dans lequel on contrecarre l'influence defavorable du faisceau de retour
JPS59148242A (ja) * 1983-02-14 1984-08-24 Matsushita Electronics Corp 受像管装置
KR920702896A (ko) * 1989-12-28 1992-10-28 로이 에이, 킬레스 증가된 비임 전류 레벨에서 교차점의 감소된 이동을 가지는 전자총 및 이의 작동방법

Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US7197308B2 (en) 2000-08-11 2007-03-27 Symantec Corporation Enabling seamless user mobility in a short-range wireless networking environment
US7113599B2 (en) 2000-09-08 2006-09-26 Symantec Corporation Location-independent packet routing and secure access in a short-range wireless networking environment
US7224979B2 (en) 2001-05-03 2007-05-29 Symantec Corporation Location-aware service proxies in a short-range wireless environment

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Publication number Publication date
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