Flat cathode ray display tube.

摘要

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. The ensure that the beam correctly enters the reversing lens (40) in its acceptance window regardless of such fields an electron-optic lens system (50) defining a series of alternate high and low voltage regions and constituting in effect a series of relay lenses is provided between the gun and the reversing lens which periodically re-focusses the beam and constrains the beam substantially along a predetermining path with respect to the reversing lens.