| 摘要 |
PURPOSE:To enable a required brightness to be obtained as well as a picture image quality to be improved by providing a control means of a beam spot shape of a picture tube, and a control means of an action of the said means corresponding to kinds of displayed signals. CONSTITUTION:An electron beam 12 shape is round when a magnetic line of force 13 is absent. A force in the direction of an arrow 14 is applied to the electron beam 12 by the magnetic line of force 13 generated by a impressed current to a coil 8. And the electron beam 12 is elongated in an up-and-down direction by a force applied in the up-and-down direction. The electron beam 12 shape is further elongated in the up-and-down direction when a current supplied to the coil 8 is high, that is, when a horizontal frequency is low. Therefore, a gap of an adjoining scanning line is eliminated and an efficient emission is obtained as a beam spot shape becomes longitudinal even a signal having a low horizontal frequency and small numbers of scanning lines is displayed. Consequently, a bright, natural, and high quality picture image can be reproduced.
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