| 摘要 |
A pair of first magnetic bodies extending in a direction of an X-axis are so disposed as to be opposed to each other on the X-axis in order to shield an external magnetic field acting on three electron beams lined side by side in the direction of X-axis. A pair of arcuated second magnetic bodies are disposed symmetric with respect to the X-axis in the vicinity of a Y-axis at a predetermined distance from a ring-shaped six-pole magnet plate. The first magnetic bodies, second magnetic bodies and six-pole magnet plate are arranged in this positional relationship, whereby a predetermined magnetic field distribution is created. Cathodes of an electron gun structure are arranged in such a position that a sum of a positive magnetic field component is substantially equal to a sum of.the negative magnetic field component on the trajectory of a center beam. Thereby, a force component acting on the center beam can be reduced without reducing force components acting on both side beams, and undesirable movement of the center beam can be prevented.
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