US2459790A

US2459790A - Indicating cathode-ray tube

Info

Publication number: US2459790A
Application number: US614527A
Authority: US
Inventors: Henri G Busignies
Original assignee: Standard Telephone and Cables PLC
Current assignee: STC PLC; Federal Telephone and Radio Corp
Priority date: 1945-09-05
Filing date: 1945-09-05
Publication date: 1949-01-25
Anticipated expiration: 1966-01-25
Also published as: FR933244A; BE482590A; CH264737A

Description

1949- H. e. BUSIGNIES 2,459,790

INDICATING CATHODE-RAY TUBE Filed Sept. 5, 1945 A TTOPI EY Patented Jan. 25, 1949 UNITED STATES PiATENT- OFFICE r, J V V 1 13 2459390"? 2 Y i it mmoa rnv'c Gammon-RAY TUBE iHenri G..Busignies,:l orest N.. Y., to Federal Telephone and Radio Corporation, .New York, N. Y., a corporation of Delaware Application September 5, 1945, Serial No.',014,5 2f7 This invention relates to cathode ray which are used for indicating purposes.

In certain systems employing cathode ray oscillograph tubes, such as for example direction finders and radar systems, the time base of the tube is rotated at a relatively low speed, such as for example, one turn per second to one turn every three or four seconds. While the direct light onthe screen of the cathode ray tube as the beam jstrikes the screenis ,often observable in'ia fairly brightly illuminated room, the after-glow cannot be seen except in relatively dark rooms. This efiect renders such indicators unsatisfactory in airplanes and other places where observation is made in a fairly brightly illuminated area.

An object of the present invention is the provision of an improved cathode ray tube for indicating purposes.

Another object of the present invention is the provision of a cathode ray tube in which the indication on the screen persists for a relatively long time and at a relatively greater intensity, as compared with the indication of the conventional cathode ray tube heretofore employed.

tubes Other and further objects of the present invention will become apparent and the invention will be best understood from the following description of an embodiment thereof, reference being had to the accompanying drawings, in which:

Fig. 1 is a schematic side elevational view of a cathode ray tube embodying my invention; and

Fig. 2 is a greatly enlarged detailed view of part of the grid of the cathod ray tube of Fig. 1.

Referring now to Fig. 1, the cathode ray tube there illustrated and generally designated by the numeral l includes an envelope 2 having the usual type of screen 3 adapted to become illuminated when impinged upon by an electron beam. Tube l includes two

electron guns

4 and 5 respectively, electron gun 4 emitting a narrow beam as indicated at 6, While electron gun 5 emits a cone-like beam as indicated at 1. Both

electron guns

4 and 5 are directed at a grid-like electrode 8 interposed between said guns and the screen, and which is shown in greater detail in Fig. 2. Electrode or grid 8 is a foraminated structure including a plurality of openings 9 through which electrons may pass. The solid part of the electrode 8 is made up of a large number, such as for example, 10,000 to 50,000, tiny particles of conductive material, that is, metallic particles l0 which are insulated from each other, for example, by being embedded as spaced intervals in a nonconductive material ll.

In operation, the beam 6 from electron gun- 4, which ispreferablyof high intensity is rotated or otherwise deflected .by the deflecting means illustrated schematically and designated by the numeral 12 so that the beam 6 moves over the surface of electrode. 8 and scans it in apredeterminedinanner. .Atthe'places on the p'erforated electrode -8 where the beam-from electron gun E has ahigh intensity, that isat the places where 'beam'fi-impinges, theparticles l0 will ac quire a negative charge. This charge canbe maintained for a given period, of for example a few seconds or longer and during this period the cone of electrons, that is, beam 1 emitted from electron gun 5 covers the whole area of the electrode 8. The stream of electrons passing through electrode 8, that is beam 1, is controlled by the potentials of the particles of the electrode 8 and therefore the amount of electrons from beam 1 passing through electrode 8 will be so controlled as to reproduce on the screen 3 an image which will depend upon the charges accumulated on the electrode 8 due to the action of the electron gun 4. It will therefore be seen that the image impressed upon the electrode 8 by electron gun 4 can be maintained visible on the screen as long as the charges of all the particles are maintained. The progressive discharge of these particles is controlled by suitable choice of the non-conductive material II and the attachment of the electrode 8 to the rest of the tube structure, so that the charges dissipate at a predeterminated rate. 7

It is preferred to so arrange the

electron guns

4 and 5 in relation to screen 3 that While electron gun 5 is aimed toward the screen, electron gun 4 is so aimed that any of its electrons passing through electrode 8 miss the screen. For this purpose the envelope 2 may be bent as indicated at l3 and the

guns

4 and 5 arranged in any suitable way, such as for example as illustrated in Fig. 1; Conventional means may be employed to collect and return the electrons emitted from the electron guns.

While I have described above the principles of my invention in connection with specific apparatus, it is to be clearly understood that this description is made only by way of example and between said means and said screen, a plurality of metallic particles disposed, in random fashion, on said plate on the side thereof facing said means, and means for conditioning said electrode so as to p mit the passage of electrons only through selected ones of the perforations in said plate.

2. A cathode ray: tube comprising means for producing an electron beam, a fluorescent screen arranged in the path of said beam, a perforated plate of insulating material, saidplatedisposed between said means and said screen, a plurality of metallic particles embeddedi 1m said plate on the side thereof facing said meanss-saiil'particles disposed in random fashion, and-means for producing an electrostatic charge on the metallicparticles on said plate adjacent selected perforations thereof to control the passage of electrons" through such selected perforations.

3; A cathode ray; tube. according-1th claim 2 wherein said electron: beam covers-substantially theentire surface ofisaid plate.

4. A cathode ray tube according to:- cla'im 2 wherein the means for producing a charge on said plateinclude means forrproducing a-relatively narrow electronbeamdirected; toward: said plate,,and means fondefiecting saidbleanntode termine theareas on said? plate: on which said narrow beam. impinges,,thereby-- chargingsthe selected areas so as to control the flow of electrons through the openings in said selected areas.

5. A cathode ray tube according to claim 2 wherein minute electrically conductive particles adjacent the selected perforations of said plate are adapted to be electrostatically charged to controfthe fibwfof eleotronsalirongirslected per- 'forationof sail' 'plate rsaid plate being adapted to dissipate the charge after a given interval.

6. A cathode ray tube according to claim 2 wheneimthe-means for producing a charge on said plate includes means for producing a relatively namoweiectron beam; directed toward said plate, and means for-deflecting said beam to determine the areas" omsaid plate on which said narrow beam-impinges-Tsaidnarrow beam being directed so that the electrons from said narrow beam passingthrough said plate do not impinge on said screen.

BUSIGNIES;

REFERENCES: CITED The following references are of record in the fi-le of this patent Young"- Oct. 21, I941