Abstract: In order to reduce contrast degradation in an electrostatically scanned flat cathode ray tube having a channel plate electron multiplier, due to back-scattered electrons entering channels remote from their origin, a coating of a material having a low back-scatter coefficient is applied over the input of the electron multiplier between the apertures therein. The surface texture of the material should be microscopically rough. The material can be applied to the first dynode or to an electrode electrically and physically connected to the first dynode. The acceptance angle of the channel plate electron multiplier may also be restricted.

Abstract: In order to reduce contrast degradation in an electrostatically scanned flat cathode ray tube having a channel plate electron multiplier due to back-scattered electrons entering channels remote from their origin, steps are taken to restrict the acceptance angle of the channel plate electron multiplier. In one arrangement means are provided on the input surface to restrict the angle of entry to a range normally associated with the addressing electron beam. In another arrangement the ready emission of secondary electrons is restricted to a predetermined arcuate portion of the input of each channel of the electron multiplier. In either arrangement stray electrons are unable to impinge upon the secondary emitting material in the channels and in consequence produce many fewer back-scattered electrons.

Abstract: In order to prevent the walls of the envelope (10) of a flat panel display tube having a large area screen from imploding, supporting walls (22) are provided to divide the interior of the envelope into a plurality of modules. Each module has its own electron beam generating means (24) for producing a low voltage, low current, intensity modulated electron beam (26) which is directed vertically upwards. A laminated channel plate electron multiplier (28) is disposed across the module and extends substantially parallel to the front and rear walls (12, 14) of the envelope. A single column of channels in the electron multiplier (28) is illustrated. The spacing of the channels determines the vertical resolution of the image produced. In order to deflect the electron beam (26) into a particular channel, a plurality of deflector electrodes (30) are disposed on the rear wall (14).

Abstract: The display tube includes an electron gun (29) which directs a low energy electron beam (30) generally parallel to a flat faceplate (14) carrying a phosphor screen (16). The beam is deflected in a plane parallel to the faceplate by deflection electrodes (38) for line scanning purposes before being reversed in direction by a reversing lens (40) and then scanned framewise over the input side of an electron multiplier (44) by further deflection electrodes (42). The low energy beam in the scanning section of the tube is susceptible to the influence of ambient magnetic fields.

Abstract: In a flat cathode ray display tube of the type comprising an envelope having parallel front and rear walls and containing implosion-preventing support walls dividing the envelope into a plurality of modules, each module including a thermionic wire electron emitter, a switching electrode arrangement having a plurality of apertures to define one of a plurality of electron beam paths directed towards a cathodoluminescent screen carried on the front wall, and a channel electron multiplier intermediate the switching electrode arrangement and the screen for beam current multiplication, and electrodes carried by the support walls for line scanning and electron acceleration, the switching electrode arrangement comprises a stack of mutually insulated electrodes associated with each aperture and selectively operable to allow or prevent electrons to pass therethrough thereby to effect frame scanning.

Abstract: A display tube of the kind in which a line-scanned, low-energy electron beam (32) is directed into a space between a planar array of elongate deflection electrodes (42) and the input side of a laminated dynode channel electron multiplier (44). The deflection electrodes are switched sequentially by driving means between two potential levels (V.sub.1, V.sub.2) so as to deflect and scan the incoming beam frame-wise over the multiplier input, the current-multiplied beam emanating from the multiplier being directed onto a screen (16) to produce a display. By ensuring that the beam acceleration voltage, Va, satisfies the relationship 1.3 Vs<Va<2 Vs, where Vs=V.sub.2 -V.sub.1, beam spot size at the multiplier input is maintained and Moiree patterning effects in the display are effectively suppressed. The multiplier input electrode and final anode of the electron gun are advantageously held at the higher (V.sub.2) of the switched potentials.

Abstract: A flat cathode ray tube comprises in an envelope (10) an electron gun (16) for generating a low energy electron beam (14) which undergoes electrostatic frame deflection by means of a pair of electrodes (22, 24). The electron beam (14) then has its energy increased by means of a double electron lens (30). The double electron lens (30) comprises a first electron lens (32) the image of which forms the object for a second electron lens (36) which provides an electron spot of acceptable size on the screen (12). Thereafter the beam undergoes line deflection in an electrostatic line deflector (40). The line deflector (40) varies the angle of entry of the electron beam into a uniform electric field formed between the screen (12) and a repeller electrode (44) where electron beam follows a parabolic trajectory to the screen (12).