| 摘要 |
PURPOSE:To obtain good resolution over all regions on a phosphor screen by correcting the shaping distortion of a beam spot caused by an electron beam that receives deflection in a ununiform deflection magnetic field. CONSTITUTION:When an electron beam 25 with a long-sideways elliptical cross section is incident on a main lens section 24, the focusing that is strong in the horizontal direction and weak in the vertical direction is actuated due to the spherical aberration of the lens and a focal point 26 in the vertical direction is faster than a focal point 27 in the horizontal direction. Like this, when the cross-sectional shape of the electron beam passing through an acceleration electrode system 12 is deflected in an elliptical form that is long in the horizontal direction following an increase of beam deflection, the focusing of the main lens section 24 on the electron beam is stronger in the horizontal direction than in the vertical direction. This event takes place so that the electron beam in the deflection magnetic field can be offset to intensely be focussed weakly in the horizontal direction and strongly in the vertical direction as the beam deflection increases. |
