US2235831A - Image converter tube - Google Patents

Image converter tube Download PDF

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Publication number
US2235831A
US2235831A US297652A US29765239A US2235831A US 2235831 A US2235831 A US 2235831A US 297652 A US297652 A US 297652A US 29765239 A US29765239 A US 29765239A US 2235831 A US2235831 A US 2235831A
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US
United States
Prior art keywords
cathode
picture
anode
spherical
electrode
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
US297652A
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English (en)
Inventor
Coeterier Frederik
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.)
Koninklijke Philips NV
Original Assignee
Philips Gloeilampenfabrieken NV
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 Philips Gloeilampenfabrieken NV filed Critical Philips Gloeilampenfabrieken NV
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Publication of US2235831A publication Critical patent/US2235831A/en
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Expired - Lifetime legal-status Critical Current

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Classifications

    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
    • H01J31/00—Cathode ray tubes; Electron beam tubes
    • H01J31/08—Cathode ray tubes; Electron beam tubes having a screen on or from which an image or pattern is formed, picked up, converted, or stored
    • H01J31/50—Image-conversion or image-amplification tubes, i.e. having optical, X-ray, or analogous input, and optical output

Definitions

  • My invention relates to image converter tubes and particularly to tubes by which radiant energy images may be intensified or transformed to radiant energy images having different characteristics.
  • a picture may be formed by projecting primary rays of light or radiant energy on a photo-electric surface or picture cathode in an electric discharge or image converter tube to liberate electrons which are focused on a fluorescent viewing screen.
  • the electrons issuing from each point of the irradiated surface of the picture cathode of an image converter tube are focused to form a picture of reduced area by establishing the electron discharge inside a spherical or substantially spherical electrode.
  • the spherical electrode is preferably transparent or provided with windows for the passage of light.
  • the spherical electrode of my tube is given a potential which is negative with respect to the picture cathode so that the electrons which are emitted by the picture cathode owing to the irradiation of the latter are accelerated in the electric field between the cathode and the fluorescent screen and are concentrated on and directed to this screen where they form a well-defined reduced reproduction of the picture projected on the cathode. Furthermore the picture may be sharply focused by varying the potential of the spherical electrode.
  • I provide an image converter tube in which still further reduction in picture area may be obtained by arranging between the picture cathode and the fluorescent screen a specially positioned annular electrode connected to a variable potential source.
  • This electrode will hereinafter be referred to as the first accelerator.
  • the first accelerator By an adequate choice of the potential of this first accelerator it is possible to ensure that the field strength in the neighborhood of the fluorescent screen increases considerably with the result that a strong refracting eifect is exerted on the electrons from the cathode.
  • By modifying the potential of the first accelerator it is possible to control still further the reduction in size of the converted image.
  • the tube comprises an evacuated envelope or bulb I, one portion of which is preferably spherical with an elongated neck section closed at the end opposite the spherical portion by a conventional press.
  • the bulb I encloses a photo cathode or picture cathode 2, preferably concave on the side facing the center of the spherical portion of the bulb and a fluorescent screen foundation electrode 3 exposed to the cathode 2 but preferably in a plane normal to the projected surface of the cathode.
  • the cathode 2 may be made of nickel or silver while the foundation electrode 3 may be of molybdenum or other refractory metal.
  • On the side of the electrode 3 exposed to the cathode I provide a fluorescent screen 4 of fluorescent material such as zinc silicate or zinc sulphide which fluoresces when bombarded by electrons.
  • the cathode 2 if not made of silver is coated with a layer of silver which is superficially oxidized and subjected to caesium as well known in the art and serves as an electron emitting cathode when connected to the negative terminal of a potential source 5 whose positive terminal is connected to the foimdation electrode 3, which acts as an anode.
  • the spherical section of the bulb l is coated on the inside with a layer 6 of conductive material, such as silver, which is in electrical contact with a supply lead 1 and constitutes the spherical electrode.
  • This silver layer may be provided simultaneously with the silver layer on the cathode 2, such as by vaporizing silver within the envelope from a source, not shown.
  • the lead 1 is connected to a potentiometer 8 which is connected in parallel with a potential source 9, and by means of this potentiometer the layer 6 may be given a potential which is negative with respect to the cathode 2. Since the layer 6 consists of conductive material such as silver and is energized from a single source such as the lead I, the layer is at a single potential over its entire surface and may be referred to as a unipotential layer or electrode.
  • the layer 6 is made photo-electrically emissive, it emits electron streams constituting an electron image having a current density varying with the areas of light and shade on the cathode.
  • the electron streams constituting an electron image of the original optical image are concentrated, the electron image being directed on the surface of the fluorescent screen to form a picture on the screen.
  • This picture is a reversed image, that is to say, the electron streams issuing from the various points of the cathode intersect each other, and this picture may be observed through the window if desired, with the aid of a magnifying lens system.
  • the picture on the fluorescent screen 4 is greatly reduced, the degree of reduction depending on the size of the bulb and on the voltage applied.
  • a bulb having a diameter of 10 cms. and with a voltage of 5000 volts between the cathode and the anode 3 a reduction of 3:1 has been obtained.
  • the potential of the spherical electrode or layer 6 with which a well-defined picture is obtained is in this case about 100 volts negative with respect to the cathode. The optimum value of the potential can easily be determined experimentally.
  • a first accelerator or annular electrode l2 which surrounds the streams of electrons from the cathode 2.
  • This electrode which acts as a first accelerator, has a separate current supply conductor I3 which, as the supply conductor M of the anode, is led through a pinch 15 of the stem N5 of the tube.
  • the annular electrode [2 is connected to a potentiometer I! which is connected in parallel with the source of current 5. It is thus possible to apply to the electrode [2 a potential lying between that of the cathode 2 and that of the anode 3. Variation of this potential permits control of the degree of reduction in the picture area on the fluorescent screen 4.
  • the reduction is greater according as the potential of the first accelerator or annular electrode l2 comes nearer to that of the cathode.
  • l8 denotes a capsule which is also arranged on the pinch I5 and serves to activate the cathode 2 in the known manner with a suitable photo electrically sensitive metal such as caesium.
  • a suitable photo electrically sensitive metal such as caesium.
  • the arrangement of the electrode 3 or fluores- 0 cent screen t with respect to the cathode need not be such, as in the example shown, that the axes of these two electrodes are exactly perpendicular to one another. They may also make smaller angles with one another without this having any influence on the desired results.
  • the annular electrode 12 should preferably be given a slightly oblique position so that the plane through the electrode is at an oblique angle to the plane of the anode 3 or fluorescent screen 4, as is shown in the drawing, in order to ensure that the electron picture is completely similar to the luminous picture on the cathode.
  • the first accelerator must be given a more oblique position with respect to the anode according as it is more remote from the anode 3. In order obtain an efficacious reduction, it must not be too remote from the anode and at any rate it must be closer to the latter than to the cathode.
  • the electrostatic surfaces have a curvature which varies with the distance from the anode 3, and since these equipotential surfaces vary in curvature, the streams of electrons emitted by the cathode are bent in their passage from the cathode to the screen 4.
  • the paths I9 and 20 Show the electron paths from two representative points on the cathode.
  • a variation in the potential difference existing between the spherical unipotential layer 6 and the cathode 2 causes the length of the electron paths between the cathode and screen to vary and consequently the focus of the electron image on the screen 4 may be adjusted by varying this potential difference.
  • An image converter tube comprising an evacuated envelope, a photo cathode adapted to receive an optical image, a luminescent anode exposed to said cathode, and a unipotential spherical electron focusing electrode enclosing said cathode and said anode and adapted when at a negative potential with respect to said cathode to focus the electron discharge from said cathode upon said anode and to direct on the surface of said anode an electron image corresponding to the optical image on said cathode.
  • An image converter tube comprising an evacuated envelope enclosing a cathode adapted to have formed thereon an optical image of an object outside the envelope, a planar anode exposed to said cathode and substantially normal to the intial direction of electrons emitted by said cathode, and a spherical unipotential electrode enclosing said cathode and anode and having portions which are pervious to the passage of light to the cathode and anode to focus the electron discharge from said cathode upon said anode.
  • An image converter tube comprising an evacuated envelope having a spherical portion, a cathode having a concave surface facing the center of said spherical portion within said envelope, a luminescent anode to become luminescent when bombarded with electrons facing the center of said spherical section and a unipotential concluctive coating on the inner surface of said spherical portion of said-envelope to direct electrons emitted from areas on said cathode to corresponding areas on said anode.
  • An image converter tube comprising a spherical envelope section, a unipotential electrode coating of electrically conductive material on the interior surface of said spherical section, a concave electron emitting cathode having a radius of curvature substantially the same as said spherical section closely adjacent a portion of the said electrode coating, the concave surface of said cathode facing the center of said spherical section, a fluorescent anode located substantially at right angles with respect to said cathode and opposite the center of said spherical section to receive electrons from said cathode, and an annular anode surrounding a small portion of the path of the electrons from said cathode to said anode positioned in a plane which intersects the plane of said anode obliquely to focus said electrons upon said fluorescent anode.
  • An image converter tube comprising an envelope having a spherical portion, a unipotential electrically conducting coating on the interior surface of said spherical portion, a cathode in the spherical portion of said envelope and having a concave surface facing the center of said spherical portion, a luminescent target having an extended surface in said envelope facing the center of said spherical portion and removed from the direct path between said cathode and the unipotential electrically conducting coating through the center of said spherical portion and an annular anode lying in a plane making an oblique angle with the plane of the extended surface of said target to focus electrons from said cathode upon said target.

Landscapes

  • Cathode-Ray Tubes And Fluorescent Screens For Display (AREA)
  • Image-Pickup Tubes, Image-Amplification Tubes, And Storage Tubes (AREA)
US297652A 1938-10-13 1939-10-03 Image converter tube Expired - Lifetime US2235831A (en)

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
NL525608X 1938-10-13

Publications (1)

Publication Number Publication Date
US2235831A true US2235831A (en) 1941-03-25

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ID=19787064

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Application Number Title Priority Date Filing Date
US297652A Expired - Lifetime US2235831A (en) 1938-10-13 1939-10-03 Image converter tube

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US (1) US2235831A (en))
BE (1) BE436646A (en))
FR (1) FR860807A (en))
GB (1) GB525608A (en))
NL (1) NL54040C (en))

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3474275A (en) * 1966-09-26 1969-10-21 Rca Corp Image tube having a gating and focusing electrode

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3474275A (en) * 1966-09-26 1969-10-21 Rca Corp Image tube having a gating and focusing electrode

Also Published As

Publication number Publication date
GB525608A (en) 1940-08-30
NL54040C (en))
BE436646A (en))
FR860807A (fr) 1941-01-24

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