| 摘要 |
PURPOSE:To enable good resolutions to be realized over the entire area of a phosphor screen by correcting the configurational distortion of a beam spot caused by an electron beam which is deflected in an uneven deflecting magnetic field. CONSTITUTION:If the sectional shape of an electron beam passing a focusing electrode system 13 is distorted into a horizontally long ellipse as the degree of beam deflection increases, the electron beam is focused by a main lens part 24 more intensely in the horizontal direction than in the vertical direction, so that the electron beam focused weakly in the horizontal direction and intensely in the vertical direction in a deflecting magnetic field according to the increase in the degree of beam deflection as mentioned above is suppressed. As a result, even a beam spot formed by a horizontally intensely deflected electron beam can be caused to have a shape close to a true circle, and the resolutions of the both sides especially as well as the areas on the diagonals of a phosphor screen are increased. Consequently, a very clear playback picture can be realized over the entire area of the phosphor screen. |
