Electron tube for electron-optical image conversion

Claim 2

An electron tube for electron optical image conversion, comprising a closed envelope of insulating material including a jacket portion having an axis of symmetry, and two opposite end portions, each provided with a transparent window arranged about said axis, a photo-cathode layer disposed adjacent the inner surface of one window, a phosphor screen layer arranged adjacent the opposite window, an anode structure mounted within said envelope around said phosphor screen and defining a passage for electrons emitted by said photo-cathode, an electrically conductive focusing coating provided on the inner surface of said tacket portion and surrounding at least a portion of said anode structure, a marginal portion of said focusing coating near said photo-cathode layer being spaced from said jacket portion to form an anNular channel therewith, and an insulating layer provided on the jacket portion within said annular channel to eliminate accidental contamination of said jacket portion by photo-cathode material.

Claim 3

An electron tube as claimed in claim 1, in which said jacket portion is of glass, said coating of insulating material including an annular glass body which is fastened to the tube wall by means of a glass material of lower melting point than that of the jacket portion, the focusing coating exceeding the inner surface of the glass body.

Claim 4

An electrode tube according to claim 1, wherein the end portion within said one window and said photo-cathode layer is made as a separate closure member and sealed to the rim of said jacket portion.

Claim 5

An electrode tube according to claim 3 further comprising a metal ring sealingly connected between said closure member and the rim of said jacket portion, at least a part of the inner surface of said metal ring forming together with the bent marginal portion of said focusing coating, said annular channel and being provided with said insulating layer.

Claim 6

An electron tube as claimed in claim 4, in which the metal ring is provided with a flange projecting inwardly and then bent over parallel to the inner surface of the ring thus forming a gutter-shaped space therewith, said flange being coated on the inner and outer sides thereof with a vitreous insulating material, the metal focusing coating exceeding the flange and being separated therefrom by the insulating layer.

Claim 7

An electron tube as claimed in claim 4 in which the said one window has a spherical surface.

Claim 8

An electron tube for electron optical image conversion comprising a closed envelope of insulating material including a jacket portion having an axis of symmetry, and two opposite end portions each provided with a transparent window arranged about said axis, a photo-cathode layer disposed adjacent the inner surface of one window, an anode structure mounted within said envelope around said phosphor screen and defining a passage for electrons emitted by said photo-cathode, an electrically conductive focusing coating provided on the inner surface of said jacket portion, a first metal ring sealing connecting said jacket portion to said one end portion having the window with the photo-cathode layer, a second metal ring sealingly interrupting said jacket portion at a distance from said first metal ring, a metal sleeve disposed within and spaced from said jacket portion, said focusing coating and one end of said sleeve being connected to said second ring, said sleeve protecting the section of the jacket portion between the two rings from accidental continuation by the photo-cathode material.

Claim 9

An electron tube for electron optical image conversion comprising a closed envelope of insulating material including a jacket portion having an axis of symmetry, and two opposite end portions each provided with a transparent window arranged about said axis, a photo-cathode layer disposed adjacent the inner surface of one window, an anode structure mounted within said envelope around said phosphor screen and defining a passage for electrons emitted by said photo-cathode, an electrically conductive focusing coating provided on the inner surface of said jacket portion, a first metal ring sealing connecting said jacket portion to said one end portion having the window with the photo-cathode layer, a second metal ring sealingly interrupting said jacket portion at a distance from said first metal ring, a metal sleeve disposed within and spaced from said jacket portion, said focusing coating and one end of said sleeve being connected to said second ring, said sleeve protecting the section of the jacket portion between the two rings from accidental continuation by the photo-cathode material.