Display arrangements

Claim 2

A display arrangement including a sealed envelope (1) containing a mesh electrode (14) positioned between an electron emissive cathode (5) arranged to emit a divergent flood beam of electrons and a fluorescent screen (3) which forms part of the envelope so that the flood beam falls upon a predetermined area of said mesh electrode; and field electrode means (7) positioned closely adjacent to the cathode for controlling the strength and polarity (with respect to the cathode) of the electric field in which the cathode is situated, so as to determine whether or not electrons are able to reach said screen to cause it to fluoresce.

Claim 3

A display arrangement including a sealed envelope containing a mesh electrode(4) positioned between an electron emissive cathode (5) arranged to emit a divergent flood beam of electrons and a fluorescent screen (13) which forms part of the envelope so that the flood beam falls upon a predetermined area of said mesh electrode; and field electrode means (7) positioned so that the cathode is between at least a part of said means and said mesh electrode, the field electrode means being positioned closely adjacent to the cathode for controlling the strength and polarity (with respect to the cathode) of the electric field in which the cathode is situated so as to determine whether or not electrons are able to reach said screen to cause it to fluoresce.

Claim 4

A display arrangement including a sealed envelope containing a mesh electrode(4) positioned between an electron emissive cathode (5) arranged to emit a divergent flood beam of electrons and a fluorescent screen (13) which forms part of the envelope so that the flood beam falls upon a predetermined area of said mesh electrode; and field electrode means (7) positioned so that the cathode is between at least a part of said means and said mesh electrode, the field electrode means being positioned closely adjacent to the cathode for controlling the strength and polarity (with respect to the cathode) of the electric field in which the cathode is situated so as to determine whether or not electrons are able to reach said screen to cause it to fluoresce.

Claim 5

A display arrangement as claimed in claim 2 and wherein a plurality of separately addressable field electrodes are provided.

Claim 6

A display arrangement as claimed in claim 2 or 3 and wherein a plurality of separately addressable cathodes are provided.

Claim 7

A display arrangement as claimed in claim 2 and wherein means are provided for confining the area of the mesh electrode, and hence the area of said screen, which can be reached by emitted electrons.

Claim 8

A display arrangement as claimed in.claim 5 and wherein said means comprise conductive plates arranged perpendicularly to the plane of the mesh electrode so as to act as stencils.

Claim 9

A display arrangement as claimed in claim 6 and wherein said conductive plates are electrically connected to said mesh electrode so as to be at the same potential, and are electrically isolated from said field electrode(s).

Claim 10

A display arrangement as claimed in claim 6 and wherein a separately addressable cathode filament is mounted immediately in front of a corresponding separately addressable field electrode, and said conductive plates are positioned so as to partially surround the filament.

Claim 11

A display arrangement as claimed in claim 6, and wherein a plurality of similar mesh electrodes are mounted side by side so as to be electrically isolated from each other, and wherein a plurality of separately addressable cathode filaments are provided in crossing relationship with said field electrodes.

Claim 12

A display arrangement as claimed in claim 3 and wherein the field electrodes are mounted end to end, and are curved so as to partially surround a common cathode filament.

Claim 13

A display arrangement as claimed in claim 10, and wherein said envelope is of an elongate tubular shape, having a flat mesh electrode mounted centrally so as to divide the envelope longitudinally into two segments, one segment containing said field electrodes and said common cathode filament, and the other segment having a coating of fluorescent material upon the interior of its curved surface to constitute said screen.

Claim 14

1 2. A method of operating a display arrangement comprising a sealed envelope containing a mesh electrode positioned between an electron emissive cathode arranged to emit a divergent flood beam of electrons and a fluorescent screen which forms part of the envelope so that the flood beam falls upon a predetermined area of said mesh electrode; and field electrode means positioned so that the cathode is between at least a part of said means and said mesh electrode, the field electrode means being positioned closely adjacent to the cathode for controlling the strength and polarity (with respect to the cathode) of the electric field in which the cathode is situated so as to determine whether or not electrons are able to reach said screen to cause it to fluoresce including the steps of applying a first predetermined potential difference between the field electrode means and the cathode so as to cause the divergent flood beam of electrons of predetermined size to be emitted from said cathode so as to cause fluorescence of said screen; and applying a second selectable predetermined potential difference between the field electrode means and the cathode so as to prevent electrons reaching the mesh electrode.

Claim 15

1 2. A method of operating a display arrangement comprising a sealed envelope containing a mesh electrode positioned between an electron emissive cathode arranged to emit a divergent flood beam of electrons and a fluorescent screen which forms part of the envelope so that the flood beam falls upon a predetermined area of said mesh electrode; and field electrode means positioned so that the cathode is between at least a part of said means and said mesh electrode, the field electrode means being positioned closely adjacent to the cathode for controlling the strength and polarity (with respect to the cathode) of the electric field in which the cathode is situated so as to determine whether or not electrons are able to reach said screen to cause it to fluoresce including the steps of applying a first predetermined potential difference between the field electrode means and the cathode so as to cause the divergent flood beam of electrons of predetermined size to be emitted from said cathode so as to cause fluorescence of said screen; and applying a second selectable predetermined potential difference between the field electrode means and the cathode so as to prevent electrons reaching the mesh electrode.