| 摘要 |
The invention relates to a cathode ray tube (100) comprising an electron source (101) having a cathode (105, 106, 107) for emitting electrons, an electron beam guidance cavity (120, 121, 122) having an input and an output aperture for concentrating electrons emitted from the cathode, a first electrode being connectable to a first power supply means for applying, in operation, an electric field having a first field strength E1 between the cathode (105, 106, 107) and the output aperture so as to allow electron transport through said electron beam guidance cavity (120, 121, 122), an accelerating grid (140) unit for accelerating the electrons leaving said cavity, and a main electron lens (150) for focusing the accelerated electrons on a display screen (170). According to the invention, said accelerating grid unit (140) further comprises a plurality of grids (G3, G4, G5) together constituting a pre-focus lens.
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