US2173498A - Hot cathode arrangement for a cathode ray tube - Google Patents

Hot cathode arrangement for a cathode ray tube Download PDF

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Publication number
US2173498A
US2173498A US110043A US11004336A US2173498A US 2173498 A US2173498 A US 2173498A US 110043 A US110043 A US 110043A US 11004336 A US11004336 A US 11004336A US 2173498 A US2173498 A US 2173498A
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United States
Prior art keywords
cathode
electron
aperture
shield
optical system
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Expired - Lifetime
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US110043A
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English (en)
Inventor
Schlesinger Kurt
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Loewe Opta GmbH
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Loewe Opta GmbH
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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
    • H01J29/58—Arrangements for focusing or reflecting ray or beam
    • H01J29/62—Electrostatic lenses
    • H01J29/622—Electrostatic lenses producing fields exhibiting symmetry of revolution
    • H01J29/624—Electrostatic lenses producing fields exhibiting symmetry of revolution co-operating with or closely associated to an electron gun

Definitions

  • Oxide spots of this nature do not always remain homogeneous as regards emission nor constant as regards form and the strength of emission.
  • the current density in the case of very bright television cathode ray tubes is much greater than usual in amplifying tube constructions.
  • the sizes of the, emissive surfaces of these cathodes cannot be increased beyond a certain dimension which is prescribed by the optical system, and currents of approximately 1 mA. are frequently taken from a cathode of .5 mm. in diameter, i. e., a current density of 4 mA.: mm. and more.
  • the object of the invention is to provide a hot cathode arrangement, which is particularly suitable for electron-optical reproduction.
  • Fig. 1 shows a simple electrode system of a cathode ray tube together with some external sources connected thereto, embodying the invention
  • Figs. 2 and 3 show modifications of the voltage supplying circuits for the cathode heating filament and for an auxiliary electrode
  • Fig. 4 shows a particular structure of the cathode arrangement with a special discharge path incorporated therein for obtaining a rectified voltage for the mentioned auxiliary electrode
  • Fig. 5 illustrates the light intensity control in a television tube designed according to the invention.
  • the optical object i. e., the object of the optical reproduction
  • the aperture of a metallic screen I in Fig. '1
  • an emissive layer 2 Behind this surface I an emissive layer 2 is provided, the surface of which may be much larger than the object point I and which is situated at a small distance from I.
  • a metallic body
  • a nickel body 2 for example a nickel body 2
  • the spacing between i and the edge of 4 is of the order of 1 mm.
  • a suction anode 5 provided in front of the perforated diaphragm I is unable to extract sufiicient emission from the cathode 2,2, even if supplied by the source 6 with a positive potential relatively to the cathode as high as approximately 200500 volts.
  • the surface of the perforated sheet I is so shaped that the combination of this lid with an anode 5 opposed thereto supplies a concentration field, which acts in the manner of a lens that is situated very close to the object and tends to concentrate the rays onto the point of the main lens, i. e., into the aperture of the main anode.
  • a conical or spherical grind l3 solves this problem, affording a preliminary concentration which may be separately varied by varying the bias of 5 at the wiper tapping 24 without simultaneous variation in the sharpness of reproduction.
  • the radius of a spherical grind it is derived by rough calculation after entering the spacing 1' between cathode and anode and on the assumption that the -volt electrons arrive in the aperture i without any appreciable speed of their be uselessly dissipated in the resistances.
  • the required value of d is found to be 1/2 mm., which means a comparatively fiat grind.
  • the spacing between the accelerating electrode 5 and the aperture I is selected to be large in comparison with d.
  • the aperture in the suction anode 5 is also selected to be large in relation to the cross section of the bundle of rays at this point-in the stated example 5 mm.
  • the location of the first refractive power viz., the condenser lens 5 /5, coincides with the location of the object i to be re produced. It is only under this condition that the adjustment of the width of the bundle of rays by the condenser does not vary the size of the image I2 projected by the main lens 8/8 of I.
  • the adjustments of the condenser lens and the main lens were 'coupled with each other to a very considerable extent.
  • Tubeshaving a cathode free of space charges, as described, have the disadvantage that the currents traversing the circuit of the space charge battery "I are 'of a strength which is a multiple of the strength of the ray currents leaving the aperture 1.
  • the cathode ray tube Upon operating the cathode ray tube with high anode potentials and upon the use .of potentiometers for obtaining the bias of 1. a considerable electric power would require to The urgent necessity accordingly arises to be able to take the powerful space charge current of the circuit 1 from a special potential source, so that the high-tension battery "fi/ID is very greatly relieved.
  • the space charge potential 7 is taken from the heating battery M, and if this is not a direct potential source but an alternating current generator the bias, in accordance with still a further feature of the invention, is derived from this generator by rectification, the rectification being performed .either by means of a separate external rectifier or preferably by means of a special hot-cathode discharge path within the tube itself and with its own built-in heating device.
  • Fig. 2 there is shown, to begin with, the most simple case of a perforated cathode heated by direct current.
  • the incandescent member heated by'a spiral filament 3 the filament 3 being so dimensioned that the heating voltage to be taken from the source M is of the amount neces sary for space charge elimination, for example 6 volts.
  • the perforated plate I is simply connected in this case with the positive pole of the heating battery I 4, whilst the negative pole is filament 3 of the cathode ray tube.
  • the anode battery 5/! of the cathode ray tube is merely loaded by the weak ray current and accordingly operates with comparatively little power consumption.
  • Fig. 3 shows a perforated cathode with alternating current operation and external rectifier.
  • a transformer winding I5 provides for the alternating current heating of the filament 3 with approximately 6 volts peak potential.
  • a detector I6 allowing the passage of current in the direction indicated a condenser I? of about 1 mf.-in the case of more than 500 mA emission the condenser I'I requires to have a higher capacityis charged positively to peak potential and its positive charge is communicated to the perforated diaphragm I.
  • the crystal detectors employed in the radio art for example the cuprous oxide detector Sirutor (passage of current up to .5 mA, permissible voltage up to 20 volts), are excellently suited to serve as the detector I6, but any other rectifier may of course be employed in place of a crystal detector.
  • FIG. 4 Particularly convenient is the form of embodiment shown in Fig. 4, in which a small hot cathode discharge path is employed for rectification of the filament voltage, the hot cathode of which discharge path receives its temperature from the An insulating tube I9, which contains a spiral filament 3, is fitted on a cylindrical copper member I8.
  • This cylindrical member heats simultaneously the emissive cathode 2 and an auxiliary cathode 20, which two cathodes are insulated against each other and have their leads passed out separately.
  • Opposite to the auxiliary cathode 20 there is situated an auxiliary anode 2
  • a cap I is fitted over the member I8 serving as a guidiing member, the plate terminating which cap acts as the perforated diaphragm and the space charge grid and may also be furnished with the aforesaid electron-optically effective grind I3,
  • a cathode of this nature accordingly has in itself 5 poles, further the indicated connections between the auxiliary cathode 20 and the outer 'member I, and between the auxiliary anode 2I or the base member I8 and the filament 3.
  • filament voltage it is not absolutely necessary to employ the filament voltage in equal amount for the elimination of the space charge.
  • Higher space charge potentials may for instance be obtained by employing additional windings at the heating transformer I5, or by theme of additional batteries or the like.
  • the light intensity control of a perforated cathode may also take place by means of a special control electrode according to Fig. 5.
  • the hot cathode 2 has a perforated diaphragm I opposed thereto, which is maintained at a constant potential relatively to the oathode, so that the aperture of l becomes the outlet point for generous emissions of low potential.
  • a special control electrode 22 is situated at a distance of about 1 mm. in front of the space charge aperture I and possesses itself an aperture of approximately the same or somewhat larger diameter, so that it remains very nearly currentless even if its potential is sl ghtly postiive in relation to the cathode.
  • the control diaphragm is coupled with the receiver 23 and effects the intensity control of space charge cathodes of this kind.
  • a reproducing electronoptical system of the kind known per se follows, in the direction away from the cathode, on an element of this nature.
  • the first plate of this electron-optical system is provided with a higher potential than the two diaphragms l and 22, so that the emerging current is conducted immediately into the electron-optical system.
  • a cathode ray tube including a picture receiving surface and an electron-optical system adapted to produce an electron image on said picture receiving surface: the combination comprising a hot cathode mounted in said tube more remote from said picture receiving surface than said electronoptical system, said cathode having an extensive emissive surface facing said electron-optical sysan apertured shield mounted in front of said emissive surface at a small distance therefrom, the aperture in said shield being centrally aligned with said emissive surface and substantially smaller than said emissive surface, a suction anode mounted in axial alignment with said shield at the side thereof remote from the oathode for causing said emissive surface to emit electrons through said aperture to adapt said aperture to form the object of the electronoptical reproduction to be efiected by said electron-optical system, the surface of said shield facing said suction anode being shaped to provide in combination with said suction anode a preliminary concentrating field for concentrating the electrons
  • a cathode ray tube including a picture receiving surface and an electron-optical system adapted to produce an electron image on said picture receiving surface: the combination comprising a hot cathode mounted in said tube more remote from said picture receiving surface than said electronoptical system, said cathode having an extensive emissive surface facing said electron-optical systern.
  • an apertured shield mounted in front of said emissive surface at a small distance therefrom, the aperture in said shield being centrally aligned with said emissive surface and substantially smaller than said emissive surface, a suction anode mounted in axial alignment with said shield at the side thereof remote from the cathode for causing said emissive surface to emit electrons through said aperture to adapt said aperture to form the object of the electron-optical reproduction to be effected by said electronoptical system, the surface of said shield facin said suction anode forming part of a hollow cone to provide in combination with said suction anode a preliminary concentrating field for concentrating the electrons leaving said aperture into said electron-optical system, and means for maintaining said shield a few volts positive in relation to said cathode for eliminating space charges from the surroundings of said cathode.
  • a cathode ray tube including a picture receiving surface and an electron-optical system adapted to produce an electron image on said picture receiving' surface: the combination comprising a hot cathode mounted in said tube more remote from said picture receiving surface than said electronoptical system, said cathode having an extensive emissive surface facing said electron-optical system, an apertured shield mounted in front of said emissive surface at a small distance therefrom, the aperture in said shield being centrally aligned with said emissive surface and substantially smaller than said emissive surface, a suction anode mounted in axial alignment with said shield at the side thereof remote from the cathode for causing said emissive surface to emit electrons through said aperture to adapt said aperture to form the object of the electron-optical reproduction to be effected by said electron optical system, the surface of said shield facing said suction anode forming part of a hollow sphere to provide in combination with said suction anode a preliminary concentrating field for concentrating the electrons
  • a cathode ray tube including a picture receiving surface and an electron-optical system adapted to p-roduce an electron image on said picture receiving surface
  • said electron-optical system including an anode member: the combination comprising a hot cathode mounted in said tube more remote from said picture receiving surface than said electron-optical system, said cathode having an extensive emissive surface facing said electronoptical system, an apertured shield mounted in front of said emissive surface at a small distance therefrom, the aperture in said shield being centrally aligned with said emissive surface and substantially smaller than said emissive surface, a suction anode mounted in axial alignment with said shield at the side thereof remote from the cathode for causing said emissive surface to emit electrons through said aperture to adapt said aperture to form the object of the electron-optical reproduction to be effected by said electronoptical system, the surface of said shield facing said suction anode forming part of a hollow 'sphere to provide in combination
  • a cathode ray tube including a picture receiving surface and an electron-optical system adapted to produce an electron image on said picture receiving surface: the combination comprising a hot cathode mounted in said tube more remote from said picture receiving surface than said electron-optical system, said cathode having an extensive emissive surface facing said electron-optical system, an apertured shield mounted in front of said emissive surface at a small distance therefrom, the aperture in said shield being centrally aligned with said emissive surface and substantially smallerthan said emissive surface, a suction anode mounted in axial alignment with said shield at the side thereof remote from the oathode for causing said emissive surface to emit electrons through said aperture to adapt said aperture to form the object of the electron-optical reproduction to be effected by said electron-optical system, the surface of said shield facing said suction anode being shaped to provide in combination with said suction anode a preliminary concentrating field for concentrating the electrons leaving said
  • a cathode ray tube including a picture receiving surface and an electron-optical system adapted to produce an electron image on said picture receiving surface: the combination comprising a hot cathode mounted in said tube more remote from said picture receiving surface than said electronoptical system, said cathode having an extensive emissive surface facing said electron-optical system, an apertured shield mounted in front of said emissive surface ata small distance therefrom, the aperture in said shield being centrally aligned with said emissive surface and substantially smaller than said emissive surface, a suction anode mounted in axial alignment with said shield at the side thereof remote from the cathode for causing said emissive surface to emit electrons through said aperture to adapt said aperture to form the object of the electron-optical reproduction to be effected by said electron-optical system, the surface of said shield facing away from said cathode being shaped to provide a preliminary concentrating field which in itself would concentrate the electrons leaving said aperture into a point disposed between said shield
  • a cathode ray tube including a picture receiving surface and an electron-optical system adapted to produce an electron image on said picture receiving surface: the combination comprising a hot cathode mounted in said tube more remote from said picture receiving surface than said electron-optical system, said cathode having an extensive emissive surface facing said electron-optical system, an apertured shield mounted in front of said emissive surface at a small distance therefrom, the aperture in said shield being centrally aligned with said emissive surface and substantially smaller than said emissive surface, means for causing said emissive surface to emit electrons through said aperture to adapt said aperture to form the object of the electron-optical reproduction to be effected by said electron-optical system, an alternating current source for supplying heating current to said cathode, auxiliary electrodes mounted inside said cathode ray tube, said auxiliary electrodes comprising a further hot cathode to form an auxiliary dicharge path energized by said alternating current source
  • a cathode ray tube including a picture receiving surface and an electron-optical system adapted to produce an electron image on said picture receiving surface: the combination comprising a hot cathode mounted in said tube more remote from said picture receiving surface than said electron-optical system, said cathode having an extensive emissive surface facing said electron-optical system, an apertured shield mounted in front of said emissive surface at a small distance therefrom, the aperture in said shieldbeing centrally aligned with said emissive surface and substantially smaller than said emissive surface, means for causing said emissive surface to emit electrons through said aperture to adapt said aperture to form the object of the electron-optical reproduction to be effected by said electron-optical system, means for maintaining said shield a few volts positive in relation to said cathode for eliminating space charges from the surroundings of said cathode and means for applying shading control potentials to said shield.
  • a cathode ray tube including a picture receiving surface and an electron-optical system adapted to produce an electron image on said picture receiving surface: the combination comprising a hot cathode mounted in said tube more remote from said picture receiving surface than said electronoptical system, said cathode having an extensive emissive surface facing said electron-optical system, an apertured shield mounted in front of said emissive surface at a small distance therefrom, the aperture in said shield being centrally aligned with said emissive surface and substantially smaller than said emissive surface, means for causing said emissive surface to emit electrons through said aperture to adapt said aperture to form the object of the electron-optical reproduction to be effected by said electron-optical system, a shading control electrode mounted in axial alignment with said shield at the side thereof remote from said cathode, means for maintaining said shield a few volts positive in relation to said cathode for eliminating space charges from the surroundings of said cathode, and means for applying shading control potentials to

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US110043A 1935-11-16 1936-11-10 Hot cathode arrangement for a cathode ray tube Expired - Lifetime US2173498A (en)

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DE489028X 1935-11-16

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Cited By (11)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2806163A (en) * 1954-08-18 1957-09-10 Rca Corp Triple gun for color television
US2888588A (en) * 1953-04-03 1959-05-26 Gen Electric Electron gun structure
US2919380A (en) * 1957-07-23 1959-12-29 Philco Corp Electron discharge devices
US2971108A (en) * 1958-09-26 1961-02-07 Sylvania Electric Prod Electron discharge device
US2991393A (en) * 1958-07-17 1961-07-04 Philips Corp High-transconductance cathode-ray tube
US3004186A (en) * 1958-09-17 1961-10-10 Zenith Radio Corp Cathode-ray tube arrangement
US3015749A (en) * 1958-07-17 1962-01-02 Philips Corp High transconductance cathoderay tube
US3016471A (en) * 1959-06-04 1962-01-09 Sylvania Electric Prod Cathode ray tube structure
US3065375A (en) * 1958-07-14 1962-11-20 Westinghouse Electric Corp Cathode ray device
US3065376A (en) * 1958-07-14 1962-11-20 Westinghouse Electric Corp Electron beam device
US3065368A (en) * 1957-12-27 1962-11-20 Westinghouse Electric Corp Cathode ray device

Cited By (11)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2888588A (en) * 1953-04-03 1959-05-26 Gen Electric Electron gun structure
US2806163A (en) * 1954-08-18 1957-09-10 Rca Corp Triple gun for color television
US2919380A (en) * 1957-07-23 1959-12-29 Philco Corp Electron discharge devices
US3065368A (en) * 1957-12-27 1962-11-20 Westinghouse Electric Corp Cathode ray device
US3065375A (en) * 1958-07-14 1962-11-20 Westinghouse Electric Corp Cathode ray device
US3065376A (en) * 1958-07-14 1962-11-20 Westinghouse Electric Corp Electron beam device
US2991393A (en) * 1958-07-17 1961-07-04 Philips Corp High-transconductance cathode-ray tube
US3015749A (en) * 1958-07-17 1962-01-02 Philips Corp High transconductance cathoderay tube
US3004186A (en) * 1958-09-17 1961-10-10 Zenith Radio Corp Cathode-ray tube arrangement
US2971108A (en) * 1958-09-26 1961-02-07 Sylvania Electric Prod Electron discharge device
US3016471A (en) * 1959-06-04 1962-01-09 Sylvania Electric Prod Cathode ray tube structure

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Publication number Publication date
FR814076A (fr) 1937-06-14
GB489028A (en) 1938-07-18

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