| 摘要 |
A flat cathode ray display tube in which an electron beam (30) is directed firstly in a rear region (24) parallel to a faceplate (14) carrying a phosphor screen (16) and then reversed to travel in the opposite direction in a front region (22) before being deflected towards, and raster scanning over, the screen. A magnetic shield (60) is provided in the rear region to shield the beam from magnetic fields entering through the faceplate over a portion of its path length in that region to reduce raster shift effects caused by such fields. This is especially useful when the electron beam in the front and rear regions is a low-energy beam, rendering it particularly susceptible to influence by magnetic fields, such beam being supplied to an electron multiplier (44) overlying the screen.
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