US3289034A - Cathode-ray tube having an auxiliary electrode between the control grid and the anode electrode - Google Patents

Cathode-ray tube having an auxiliary electrode between the control grid and the anode electrode Download PDF

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Publication number
US3289034A
US3289034A US548819A US54881966A US3289034A US 3289034 A US3289034 A US 3289034A US 548819 A US548819 A US 548819A US 54881966 A US54881966 A US 54881966A US 3289034 A US3289034 A US 3289034A
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United States
Prior art keywords
cathode
grid
electrode
anode
aperture
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Expired - Lifetime
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US548819A
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English (en)
Inventor
Weber Cornelis
Johannes Van Esdonk
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US Philips Corp
North American Philips Co Inc
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US Philips Corp
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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
    • H01J29/52—Arrangements for controlling intensity of ray or beam, e.g. for modulation

Definitions

  • This invention relates to devices comprising a cathoderay tube having an electron gun which can be operated at low control-voltages, it being possible to obtain an electron beam producing a spot of very small diameter on the fluorescent screen.
  • the invention also relates to cathode-ray tubes for such devices.
  • a fine-meshed grid electrode maintained at a low positive potential may be arranged closely in front of the cathode.
  • the positive potential is necessary to allow the passage of a suflicient flow of electrons despite the fine meshes.
  • an auxiliary electrode maintained at zero potential of a low negative potential is arranged between the said grid and the anode maintained at a high potential, so that the electron current is completely suppressed if the grid has a potential equal to that of the cathode.
  • the cross-section of the ray near the control electrode may then be determined by either the cathode surface or the aperture of the grid.
  • a positive grid has a limitation in that it starts to convey current. But if the positive potential is maintained low and the grid is made from very thin wires and arranged close to the cathode, both the number and the velocity of the electrons striking the grid wires may be limited, so that their energy is low and the heating of the grid remains within permissible limits.
  • the grid is usually wound on a thin plate secured to a rigid frame.
  • the positive grid potential involves the further disadvantage that straying of the electrons at right angles to the grid wires is apt to occur so that the electron spot on the fluorescent screen of the tube is elliptically deformed as a function of the instantaneous value of the control voltages.
  • a device comprising a cathode-ray tube having an electron gun constituted by a cathode, a grid electrode maintained at a low positive potential is arranged closely in front of the cathode, an auxiliary electrode maintained at a negative potential, and an anode maintained at a high positive potential, in which steps have been taken to ensure that the cathode-ray, upon leaving the grid, has a predetermined crosssection and produces a spot of very small size on a fluorescent screen, so high a negative potential is applied to the auxiliary electrode that the space potential at the grid surface is substantially equal to the positive potential of the grid, and the aperture of the auxiliary electrode has a diameter at least about thrice that of the active grid surface.
  • the negative potential of the auxiliary electrode is higher than 50 volts and usually from Patented Nov. 29, 1936 "ice 100 to 150 volts negative with respect to the mean cathode potential, dependent upon the anode voltage and the dimensions and arrangement of the electrodes of the gun.
  • the cross-section of the cathode ray upon leaving the grid may be determined by the electron-emissive cathode surface, or by the aperture in the grid electrode itself.
  • FIGURE 1 shows a device according to the invention
  • FIGURE 2 shows a detail of this device
  • FIGURE 3 shows a detail of another embodiment of the invention.
  • the reference numeral 1 indicates the envelope of a cathode-ray tube.
  • the tube contains an electron gun comprising a cathode 2, a grid 3, an anode 4, an auxiliary electrode 5 and a screen electrode 6, and further a fluorescent screen '7.
  • the control voltage is applied in this case between ground and the cathode 2.
  • the cathode 2 has a surface area which corresponds to the cross-section of the beam and thus determines the cross-sections near the grid. Interference resulting from electrons released from the margin of cathode 2 are avoided since emission of electrons from the margin is suppressed by applying a negative potential which is not critical, and may be from 2 to 20 volts negative to screen electrode 6 tightly surrounding the electron-emissive surface. That surface of the screen electrode which is adjacent the grid may structurally in the best way be co-planar with the active surface of the cathode.
  • grid 3 has a slightly positive potential, for example of 10 volts, and steps have been taken that the space potential in situ is substantially equal to the grid potential, it is as if the grid wires were not present and the electrons are substantially not deflected by the grid wires. Due to the small distance between grid 3 and cathode 2 of, for example, from to microns and the low positive potential of grid 3, the electrons striking the grid wires have a low velocity and hence a low energy (about 1 mw. in this case) so that disadvantageous heating of the thin grid wires does not occur. Since the grid wires substantially do not produce a lens effect and the space potential is substantially equal to the grid potential, the electrons are focussed at a single focus between auxiliary electrode 5 and anode 4, as shown in FIGURE 2.
  • the control is sensitive.
  • the space potential at the grid still to be made sufficiently low by applying a high negative potential to auxiliary electrode 5.
  • the aperture of the auxiliary electrode 5 must have a diameter at least thrice the diameter of the ray at the grid 3.
  • a difficulty involved in the structure of FIGURE 2, in which the cross-section of the cathode ray is determined by the cathode surface, is that the cathode must be positioned very accurately in the center line of the gun.
  • the cathode has, in a manner known per se, a surface area, larger than the cross-section of the ray near the grid, which cross-section is determined by the open portion of the grid, as shown in FIGURE 3.
  • the cathode 8 need now be positioned only at the correct distance from grid 9, but in a lateral direction the mounting is not critical.
  • the grid 9 comprises ten thin wires provided over the aperture of a thin metal plate 10.
  • the plate 10 must be thinner than one tenth of the diameter of the ray in situ, since the edge of the aperture in the plate otherwise causes interference in the electron paths.
  • the aperture of grid 9 is in this case 0.4 mm. in diameter, the grid wires 7 are 7 microns thick, the plate 10 is 10 microns thick and the pitch of the grid Wires is 40 microns.
  • the plate 10 itself is secured to a rigid grid frame 11 the aperture of which is such that the distance between its edge and the cathode ray is at least twice the thickness of the frame.
  • the aperture of frame 11 has a diameter of 2 mm.
  • This distance between grid 9 and cathode surface 8 is 90 microns, the distance between auxiliary electrode and cathode 8 is 650 microns.
  • the cylindrical part of auxiliary electrode 5 has a diameter of mm. and the smallest distance between anode 4 and cathode 8 is about 5 mm.
  • the cathode ray has a single substantially circular punctiforxn focus 12, in contrast to the case where the grid is not maintained at the space potential locally prevailing and the focus is deformed elliptically.
  • a focus of unduly large size occurs if the apertures of the electrode parts 5, 10 and 11 are not large enough, as is the case in most conventional electron guns. Too large an aperture of electrode 5 is disadvantageous, however, since in this case its potential must be much more negative for obtaining the desired low space potential near the grids 3 and 9 respectively.
  • a device according to the invention permits of substantially avoiding the disadvantageous deformation of the luminous spot on screen 7, while a control voltage less than 10 volts suffices for complete modulation of the beam current.
  • An image-reproducing device comprising a cathoderay tube having a beam-forming electrode system comprising a cathode, a first anode, means to apply a positive potential to said anode, a disc-shaped control electrode having an aperture for the passage of a cathode-ray positioned in proximity to the cathode between the anode and cathode, a plurality of parallel wire conductors extending across said aperture in said control electrode, means to apply to said control electrode a positive potential less than that applied to said anode, an auxiliary electrode having an aperture whose diameter is at least three times that of the cathode-ray at the control electrode positioned between said control electrode and said anode, and means to apply a negative potential of more than 50 volts to said auxiliary electrode.
  • An image-reproducing device comprising a cathoderay tube having a beam-forming electrode system comprising a cathode having an electron-emissive surface larger than the cross-section of a cathode-ray, a first anode, means to apply a positive potential to said anode, a discshaped control electrode having an aperture for the passage of a cathode-ray positioned between the anode and cathode and in proximity to the cathode, said disc having a thickness which is less than one-tenth of the diameter of the cathode-ray, the cross-section of which is determined by the aperture in the disc, 21 frame supporting said disc having an aperture the edge of which is spaced from the cathode-ray a distance which is at least twice the thickness of the frame, a plurality of parallel wire conductors extending across the aperture in said disc, means to apply to the control electrode a positive potential lower than that applied to the anode, an auxiliary electrode having an aperture whose diameter is at least three times that of

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  • Cathode-Ray Tubes And Fluorescent Screens For Display (AREA)
  • Electrodes For Cathode-Ray Tubes (AREA)
US548819A 1961-05-24 1966-05-04 Cathode-ray tube having an auxiliary electrode between the control grid and the anode electrode Expired - Lifetime US3289034A (en)

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
NL265121 1961-05-24

Publications (1)

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US3289034A true US3289034A (en) 1966-11-29

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US548819A Expired - Lifetime US3289034A (en) 1961-05-24 1966-05-04 Cathode-ray tube having an auxiliary electrode between the control grid and the anode electrode

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US (1) US3289034A (de)
CH (1) CH412121A (de)
DE (1) DE1236085B (de)
DK (1) DK103358C (de)
ES (1) ES277527A1 (de)
GB (1) GB995561A (de)
NL (2) NL265121A (de)

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3439222A (en) * 1965-07-19 1969-04-15 Thomson Houston Comp Francaise Electronic zoom image intensifier tube
US3678329A (en) * 1969-06-30 1972-07-18 Sony Corp Cathode ray tube

Families Citing this family (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
NL8302754A (nl) * 1983-08-04 1985-03-01 Philips Nv Kathodestraalbuis.

Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2225455A (en) * 1937-07-07 1940-12-17 Siemens App Und Maschinen Gmbh Cathode ray device
US2852716A (en) * 1954-07-14 1958-09-16 Gen Electric Cathode ray tube and electron gun therefor
US2922072A (en) * 1957-12-05 1960-01-19 Sylvania Electric Prod Image reproduction device
US2975315A (en) * 1957-03-13 1961-03-14 Rauland Corp Cathode-ray tube
US2983842A (en) * 1959-06-23 1961-05-09 Zenith Radio Corp Electrode system

Family Cites Families (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
BE513449A (de) * 1951-08-11

Patent Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2225455A (en) * 1937-07-07 1940-12-17 Siemens App Und Maschinen Gmbh Cathode ray device
US2852716A (en) * 1954-07-14 1958-09-16 Gen Electric Cathode ray tube and electron gun therefor
US2975315A (en) * 1957-03-13 1961-03-14 Rauland Corp Cathode-ray tube
US2922072A (en) * 1957-12-05 1960-01-19 Sylvania Electric Prod Image reproduction device
US2983842A (en) * 1959-06-23 1961-05-09 Zenith Radio Corp Electrode system

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3439222A (en) * 1965-07-19 1969-04-15 Thomson Houston Comp Francaise Electronic zoom image intensifier tube
US3678329A (en) * 1969-06-30 1972-07-18 Sony Corp Cathode ray tube

Also Published As

Publication number Publication date
NL265121A (de)
NL130957C (de)
GB995561A (en) 1965-06-16
DE1236085B (de) 1967-03-09
CH412121A (de) 1966-04-30
ES277527A1 (es) 1962-08-16
DK103358C (da) 1965-12-20

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