US2306663A - Net control of cathode ray tubes - Google Patents

Net control of cathode ray tubes Download PDF

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Publication number
US2306663A
US2306663A US239173A US23917338A US2306663A US 2306663 A US2306663 A US 2306663A US 239173 A US239173 A US 239173A US 23917338 A US23917338 A US 23917338A US 2306663 A US2306663 A US 2306663A
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Prior art keywords
diaphragm
cathode
net
control
aperture
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US239173A
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Schlesinger Kurt
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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
    • H01J29/52—Arrangements for controlling intensity of ray or beam, e.g. for modulation

Definitions

  • the cathode surfaces of television tubes were spot-like in form, i. e. had a diameter of approximately 0.5 mm.
  • the modulation of the ray currents was possible by means of a diaphragm aperture of approximately 1 mm. in diameter closely surrounding the cathode.
  • the large-surface cathode has been adopted, which has a diameter of 1-2 mm. The emission of these large surfaces is first collected by a system of electric acceleration lenses into a much smaller point, the so-called cross-over point, and the latter is then reproduced on the screen.
  • a cathode behind a control net supplies electronic rays of particular distribution of energy, which considerably differs from the thermal distribution according to Maxwell. It is accordingly found that the treatment of net controlled electronic rays is not possible with the same optical systems which have been employed for the free surfaces of hot cathodes. If the concentration of large-surface cathodes with net control in a common focal point is to be successful, it is therefore necessary in conjunction with the net control to develop special electronoptical methods.
  • the net control is carried out substantially within the range of positive grid biasses.
  • the normally strong grid currents occurring in this connection are considerably reduced by production of the net from the finest tungsten wire obtainable, there being a ratio of 1:10 or less between the diameter of the Wire and the Width of mesh.
  • the Width of mesh is so great and the distance from the first anode so small that all of the electrons in the free opening of the meshes are sucked up entirely into the ray and do not pass to the wire net.
  • Fig. 1a there is shown the plan view of a control net for cathode ray tubes, such as has been developed by the applicant.
  • a circular cathode having an emissive surface of approximately 1 square millimetre.
  • the cathode is designated l and the spot of oxide embedded in the same is designated 2.
  • This useful surface of 1 square millimetre in size is divided by 2 X 4 wires (3) into, say, 10 fields.
  • the wires have a relative spacing a of approximately 0.3 mm.
  • the shading portion of the surface of the wire on the controlled area amounts to approximately 2d/a per unit of area, d being the thickness of the wire. If this shading proportion is to be less than 10%, the thickness of the wire (1 must be made equal to 0.015 mm.
  • a layer 4a As material there is preferably employed a heat resisting material, such as platinum or tungsten.
  • the cathode can conveniently be furnished with a surface curved in the manner of a hollow reflector.
  • nets having the very small shading factor of approximately 10% can b controlled into the positive range of up to approximately 30 volts positive bias without consuming in interfering fashion large proportions of the total emission.
  • the suction of the total mesh emission with anodes having a potential of approximately 200 volts is accordingly still possible at a distance of several millimetres away from a net of this kind, so that 80-90% of the emission of approximately 1-2 ma. per square millimetre obtainabl in the case of positive grid biasses is supplied to the ray.
  • a new electron-optical system which produces a real reduced image of the object of reproduction in or near the intersection-point diaphragm.
  • all difiiculties which resided more particularly in a complete unreliability as regards selection of the electrode spacing of the concentration system and in the impossibility of keeping the angle of divergence of the rays small when leaving the intersection-point diaphragm are solved at one go, as by means of th known laws of electron-optical reproduction this optical system is also now under control.
  • Fig. 2 there is shown a typical electronoptical system of this kind such as can be employed in conjunction with net control of all kinds.
  • an electric lens 6 which in the present case merely requires to be in th form of an aperture lens with acceleration of the ray, as it is only with lenses of this kind that with utilisation of the root-from-potential factor in the case of reasonably small object space the requisite strong reductions of approximately 1210' can be obtained.
  • the lens aperture 0 is selected to be at most equal to the useful cathode surface of 1.
  • 0 and Z are definitely determined in conjunction with the remaining tube construction, length of the tubular member, position of the main lens etc. Care accordingly requires to be taken that so far as possible all electron rays reach the opening 0.
  • a second condensing lens 1 This lens must be located at a distance l1 from the lens 5, which distance allows the lens aperture to be reproduced according to the known laws of acceleration lenses on to the dimensions of the intersection-point diaphragm 5.
  • the aperture 01 of the lens I must be larger than the net or cathode surface. The distance from the latter amounts to approximately 1 mm.
  • the potential 62 which is conveniently tapped at a common potentiometer 9. a otential. Qf. lemen 7 c n. e o d at w h the loss of current in relation to the lens 6 is at a minimum or is even reduced to zero.
  • a suitable position of 01 in relation to g is found empirically, so that the already weak anode fields are not additionally weakened by the bias of i.
  • Th condensing lens 1 can be omitted and it is possible to manage with the lens field of 5 alone.
  • the spacing Z2 between the control grid g and the lens 5 requires to be determined empirically. The smaller Z2 is selected to be, the better is the suction of the mesh electrons into the ray owing to increasing field intensity on the part of the diaphragm 6, which in The arrangement according to Fig. 3a appears to be more simple than the arrangement with intermediate diaphragm i according to Fig.
  • the object spacing Z2 between the object of reproduction and the lens 6 is of a fixed kind by reason of an auxiliary requirement, viz, the preliminary concentration, so that it is not possible to obtain any desired scale of reproduction between cathode l and diaphragm 5.
  • the cathode surface I that its image exactly fills out the diaphragm aperture 5, i. e. it is not possible to employ cathode surfaces of a desired size.
  • the method according to Fig. 3a is capable of being employed more particularly for simple tubes of medium output.
  • the cylinder 8a can either be mechanically connected with the diaphragm supporting the net, as shown in Fig. 3a, or it can be designed in the form of a separate electrode, as illustrated by Fig. 3b, in which case it is preferably connected with the potential of the cathode.
  • the distances Z2 can be determined in each case experimentally. For cathodes having a surface of 1 square millimetre and nets as shown in Fig. 10. there are to be found in practice approximately the following values:
  • a cathode ray tube comprising a cathode having a circular emissive surface, one apertured control diaphragm mounted in front of said cathode, an apertured object diaphragm the size of the aperture of which amounts to approximately 1/ 10 of the size of said emissive surface, and an electron optical preconcentrating system adapted to focus the cathode ray in the aperture of said object diaphragm, said preconcentrating system consisting of said cathode, said control diaphragm, said object diaphragm, a cylindrical electrode mounted adjacent to said control diaphragm at its side facing said object diaphragm, and a further apertured diaphragm mounted between said cylindrical electrode and said object diaphragm, the diameter of said cylindrical electrode being larger than the diameter of the aperture of said control diaphragm, the aperture of said further dia
  • a cathode ray tube comprising a cathode having a circular emissive surface, one apertured control diaphragm mounted in front of said cathode, an apertured object diaphragm, and an electron opticalpreconcentrating system adapted to focus the cathode ray in the aperture of said object diaphragm, said preconcentrating system consisting of said cathode, said control diaphragm, said object diaphragm, and two further apertured diaphragms mounted between said control diaphragm and said object diaphragm, the apertures of all of said diaphragms being circular and so dimensioned that their diameters decrease in the order 1 in which said diaphragms follow each other in the direction towards said object diaphragm, the size of the aperture of said object diaphragm being approximately equal to 1% of the size of said emissive surface, the aperture of said control diaphragm being at least as large a said emissive

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  • Electrodes For Cathode-Ray Tubes (AREA)
US239173A 1938-02-05 1938-11-05 Net control of cathode ray tubes Expired - Lifetime US2306663A (en)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
DE220849X 1938-02-05
DE20338X 1938-03-02

Publications (1)

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US2306663A true US2306663A (en) 1942-12-29

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US239173A Expired - Lifetime US2306663A (en) 1938-02-05 1938-11-05 Net control of cathode ray tubes

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US (1) US2306663A (en(2012))
BE (1) BE432560A (en(2012))
CH (1) CH220849A (en(2012))
FR (1) FR849846A (en(2012))

Cited By (10)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2644906A (en) * 1951-08-11 1953-07-07 Gen Electric Electron beam discharge device
US2835838A (en) * 1953-07-18 1958-05-20 Philips Corp Cathode-ray tube
US2867687A (en) * 1954-09-15 1959-01-06 Gen Electric Cathode ray reproduction tube having auxiliary function of synchronizing signal separation
US2902623A (en) * 1956-08-17 1959-09-01 Rca Corp Electron gun structure
US2907916A (en) * 1956-08-17 1959-10-06 Rca Corp Electron gun structure
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
US3049641A (en) * 1959-05-08 1962-08-14 Gen Electric High transconductance cathode ray tube
US3143685A (en) * 1961-07-24 1964-08-04 Multi Tron Lab Inc Character display cathode ray tube
US3293479A (en) * 1963-09-11 1966-12-20 Ultra low noise travelling wave tube having a grid voltage

Families Citing this family (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE1076827B (de) * 1952-05-24 1960-03-03 Telefunken Gmbh Elektronenstrahlerzeugungssystem fuer Kathodenstrahlroehren

Cited By (10)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2644906A (en) * 1951-08-11 1953-07-07 Gen Electric Electron beam discharge device
US2835838A (en) * 1953-07-18 1958-05-20 Philips Corp Cathode-ray tube
US2867687A (en) * 1954-09-15 1959-01-06 Gen Electric Cathode ray reproduction tube having auxiliary function of synchronizing signal separation
US2902623A (en) * 1956-08-17 1959-09-01 Rca Corp Electron gun structure
US2907916A (en) * 1956-08-17 1959-10-06 Rca Corp Electron gun structure
US2975315A (en) * 1957-03-13 1961-03-14 Rauland Corp Cathode-ray tube
US3049641A (en) * 1959-05-08 1962-08-14 Gen Electric High transconductance cathode ray tube
US2983842A (en) * 1959-06-23 1961-05-09 Zenith Radio Corp Electrode system
US3143685A (en) * 1961-07-24 1964-08-04 Multi Tron Lab Inc Character display cathode ray tube
US3293479A (en) * 1963-09-11 1966-12-20 Ultra low noise travelling wave tube having a grid voltage

Also Published As

Publication number Publication date
BE432560A (en(2012)) 1939-03-31
FR849846A (fr) 1939-12-02
CH220849A (de) 1942-04-30

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