US2887595A - Television camera tube - Google Patents

Television camera tube Download PDF

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Publication number
US2887595A
US2887595A US583970A US58397056A US2887595A US 2887595 A US2887595 A US 2887595A US 583970 A US583970 A US 583970A US 58397056 A US58397056 A US 58397056A US 2887595 A US2887595 A US 2887595A
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US
United States
Prior art keywords
tube
coating
image
electrode
cesium
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
US583970A
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English (en)
Inventor
Tijs Willem Van Rijssel
Boers Martinus Will Augustinus
Maartens Johannes Hen Josephus
Boerman Jan Rigte
Kuhl Walter Heinrich
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.)
US Philips Corp
North American Philips Co Inc
Original Assignee
US Philips Corp
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 US Philips Corp filed Critical US Philips Corp
Application granted granted Critical
Publication of US2887595A publication Critical patent/US2887595A/en
Anticipated expiration legal-status Critical
Expired - Lifetime legal-status Critical Current

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Classifications

    • 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
    • H01J29/02—Electrodes; Screens; Mounting, supporting, spacing or insulating thereof
    • H01J29/10—Screens on or from which an image or pattern is formed, picked up, converted or stored
    • H01J29/36—Photoelectric screens; Charge-storage screens
    • H01J29/39—Charge-storage screens
    • H01J29/41—Charge-storage screens using secondary emission, e.g. for supericonoscope

Definitions

  • the invention relates to a television camera tube of the kind in which a charge pattern is produced by secondary emission.
  • the tube comprises a photo-electric cathode. Electrons set free from this cathode by projecting a luminous image onto it are accelerated in the tube and focused onto an image electrode, where they produce secondary emission, owing to which a charge pattern corresponding to the luminous image is produced on the side of the image electrode facing the photoelectric cathode (image side) It is known that the image electrode of such a camera tube may be made of a substance which permits an electric charge to 4leak from one side of the electrode to the other.
  • the specic resistance of this substance should be within the range from 109 to 1012 ohm-cm.
  • so-called conductive glass is particularly suitable, an example being the glass known in the United States of America as G-B glass, exhibiting a specific resistance of about 5 X 101 ohm-cm.
  • This phenomenon becomes manifest with an increase in the collector accelerating voltage, i.e. the voltage at which the secondary electrons are conducted away as completely as possible to the collector.
  • the invention provides means to obviate this disadvantage and to obtain a higher efficiency and longer lifetime of the tube.
  • a television camera tube which tube comprises cesium and is provided with an image electrode of conductive glass, on which secondary emission produced by electrons emanating from a photo-electric cathode produces a charge pattern corresponding to a luminous image projected onto the photoelectric cathode and which is provided on the image side with a thin secondary-emissive layer (referred to hereinafter as the coating), this layer consists mainly of an inorganic sodium or lithium-halogen compound.
  • the insulating image electrode of a camera tube operating with an electron beam focused on this electrode, where it sets free secondary electrons may be constituted by an insulating layer of chloride or bromide of one or more alkali metals, for example KCl or NaCl, which is applied to a metal electrode. If necessary, an insulating layer for example of mica may be sandwiched between the said layer and the metal electrode.
  • a camera tube has furthermore been described, of which the image electrode is constituted by a thin insulating or semi-conductive layer, which may be made of an alkali halogenide and which is metal-coated on the rear side. This image electrode is scanned on the metalcoated side by rapid electrons which must render the image electrode conductive.
  • the invention may be carried into effect by using as substance for the coating a chlorine compound, such as sodium chloride.
  • cryolite sodium-aluminum uoride
  • atoms of a trivalent, ilumine-binding metal are applied to the coating containing a fluoride compound, the quantity of this metal being such that the surface conductivity and the secondary-emission coeicient of the coating are substantially not affected and that the majority of the fluorine atoms added initially to the sodium or lithium atoms in the coating are bound. It is thus ensured that during the operation of the tube free iiuorine atoms produced by secondary emission of the coating are bound with certainty in the coating, so that they do not emerge from the coating and Wander through the tube.
  • Trivalent metals suitable to this end are, for example, antimony, bismuth, indium and arsenic. Use is preferably made of antimony.
  • the atoms of this metal form, on the coating, a compound with the available cesium atoms, so that a compound having a comparatively low electrical conductivity is obtained. Even in the case of a comparatively large quantity of antimony on the coating the surface resistance thereof is little affected. A further advantage of antimony is that it hinders little the movement of the primary and secondary electrons striking the coating.
  • the part having the smaller diameter is closed by a at ,glass bottom 6, to the inner side of which is applied thephotorelectric cathode 7.
  • the cathode may, as usual, be made of antimony activated by cesium.
  • Reference numeral 8 designates an optical system, by means of which a luminous image can be projected onto the photoelectric cathode.
  • a small quantity of antimony is applied to the coating 1S.
  • the antimony may be applied directly after or, if desired, partly simultaneously with the Vapplication 'by vaporisaton of the cryolite of the coating 15.
  • Tlhe quantity of antimony applied is about 1% by weight of the applied quantity of cryolite in the coating 15. This quantity of antimony does not introduce an kappreciable change of the electrical surface re- ⁇ sistance of the coating 15, so that the image sharpness is not affected.
  • the secondary-emission coeticient of thacoating appears to be ⁇ slightly higher owingto the antimony; this is believed to be due to a reduction in emission potential, owing tothe formation of an antimonycesium compound on the surface of the coating 1S, the cesium, of course, originating from the photo-cathode 7.
  • an electrode system 10 which serves to produce an electron beam of definite intensity.
  • the axis of this system is directed to the centre of the image electrode 5.
  • the wall of the tube has a conductive coating 13, which is electrically connected to an annular collector 14, ar-
  • the image electrode is formed by a conductive glass layer of about 60p. applied to the metal supporting plate 4.
  • the ⁇ specic resistance of this glass is about 1011 ⁇ ohm-cm. under the conditions of operation of the tube.
  • cryolite 15 On the image side the conductive glass is coated with a layer of cryolite 15 of about 500 A. in thickness, precipitated from the Vapour phase.
  • This layer serves as a store for, or supply of, cesium, but provides at the same time that no excess of cesium vapour is contained in the tube, which wouldV be harmful to the sensitivity of the photo-electric cathode.
  • the cesium is adsorbed by Vthe gold layer when cesium vapour is introduced into the tube during manufacture.
  • the gold layer keeps the cesium away from the electrode system 10.
  • the current conductor 3 is connected through a load resistor 17 to the negative terminal of a direct-current source 18, the positive terminal of which is connected ⁇ to the coating 13 and hence also to the collector 14, so
  • the secondary-emission coeflicient of the cryolite layer 15 is particularly high. ⁇ Values between 9 and 11 are found. These high valies are also ascribed to the presence of cesium in the tube. Cesium ⁇ adheres readily to antimony and ⁇ halogenide ions, particularly to those of fluorine, which substance is contained in the cryolite. For a large part the favourable properties of the tube according to the invention may be due to these conditions.
  • the ⁇ tube should contain cesium.
  • this substance is provided in the photo-electric cathode. If this is not the case, a sepa- ⁇ rate supply ofcesium ⁇ can be provided. This provision may, otherwise, also be made when the photo-electric cathode already contains cesium, since experiments have shown that an excessively small supply of cesium in the tube may imply that after some time such a quantity of cesium may be withdrawn from the photo-cathode that' the effect of this cathode falls ctt.
  • a cesium supply is formed by the gold layer 16 inthe side tube ⁇
  • the coating of the tube according to the invention contains fluoine, as is the case with the example described, the spreading of fluorine atoms affecting the photo-electric cathode in the tube ⁇ is avoided with certainty by applying to the coating by vaporisation a small quantity of atoms of a trivalent, ilumine-binding metal.
  • a metal may, for example, be antimony, bismuth, indium or arsenic: use is preferably made of antimony, as is indicated above in the description of the example.
  • Camera tubes for television exhibit rather often a troublesome phenomenon, referred to as inscription
  • This phenomenon consists inthat during the use of the tube the coeflicient of the secondary emission is changed at those areas ofthe image electrode which have been loaded most. This drawback may sometimes be obviated or at least reduced by taking the tube out of operation for some time.
  • Cryolite has the favourable property that it does not or substantially not exhibit the aforesaid phenomenon of inscription Since it is, moreover, readily precipitated from the vapour phase in the tube itself on the con ductive glass, it is an excellent material for the manufacture of the secondary-emissive coating.
  • a television camera tube comprising an envelope and inside said envelope the combination comprising a photo-electric cathode and image electrode cooperating to establish a charge pattern on said image electrode corresponding to a televised object, said image electrode including a conductive glass member and a thin, secondary-electron-emissive coating thereon comprising essentially an inorganic halogen compound containing an alkali metal selected from the group consisting of sodium and lithium, Said tube also containing cesium.
  • a television camera tube comprising an envelope and inside said envelope the combination comprising a photo-electric cathode containing cesium and an image electrode cooperating to establish a charge pattern on -saidirnage electrodecorresponding to a televised object; ⁇ said image electrode including a glass member having a resistivity within the range from 109 to 1012 ohm-cm..
  • a television camera tube comprising a photo-electric cathode containing cesium and an image electrode, said image electrode being constituted of a glass member having a resistivity in the range of 109 to 1012 ohm-cm., and a thin cryolite coating on said glass member.

Landscapes

  • Image-Pickup Tubes, Image-Amplification Tubes, And Storage Tubes (AREA)
US583970A 1955-05-14 1956-05-10 Television camera tube Expired - Lifetime US2887595A (en)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
NL341862X 1955-05-14
NL140356X 1956-03-14

Publications (1)

Publication Number Publication Date
US2887595A true US2887595A (en) 1959-05-19

Family

ID=26643458

Family Applications (1)

Application Number Title Priority Date Filing Date
US583970A Expired - Lifetime US2887595A (en) 1955-05-14 1956-05-10 Television camera tube

Country Status (5)

Country Link
US (1) US2887595A (xx)
CH (1) CH341862A (xx)
DE (1) DE1014155B (xx)
FR (1) FR1153190A (xx)
NL (2) NL104633C (xx)

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3313975A (en) * 1964-07-06 1967-04-11 Hughes Aircraft Co Electron impervious flexible shield member for electron discharge tubes
US3736460A (en) * 1971-06-28 1973-05-29 Columbia Broadcasting Syst Inc Off-axis return beam tube

Families Citing this family (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE1282062B (de) * 1966-05-28 1968-11-07 Fernseh Gmbh Verfahren zur Herstellung von Superorthikonroehren mit einer Speicherelektrode aus elektronisch leitendem Glas

Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2535817A (en) * 1942-09-14 1950-12-26 Nat Union Radio Corp Electrooptical dark trace storage tube
US2547638A (en) * 1948-12-18 1951-04-03 Raytheon Mfg Co Image storage tube
CA510784A (en) * 1955-03-08 Bruining Hajo Television camera tube

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CA510784A (en) * 1955-03-08 Bruining Hajo Television camera tube
US2535817A (en) * 1942-09-14 1950-12-26 Nat Union Radio Corp Electrooptical dark trace storage tube
US2547638A (en) * 1948-12-18 1951-04-03 Raytheon Mfg Co Image storage tube

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3313975A (en) * 1964-07-06 1967-04-11 Hughes Aircraft Co Electron impervious flexible shield member for electron discharge tubes
US3736460A (en) * 1971-06-28 1973-05-29 Columbia Broadcasting Syst Inc Off-axis return beam tube

Also Published As

Publication number Publication date
NL104633C (xx)
FR1153190A (fr) 1958-03-03
DE1014155B (de) 1957-08-22
NL197262A (xx)
CH341862A (de) 1959-10-31

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