| 摘要 |
PURPOSE:To obtain relatively uniform picture quality over all scanning surfaces by arranging the target position of a tube in a uniform magnetic field while avoiding nonuniform magnetic field to be occurred at an end portion of a focussing magnetic field. CONSTITUTION:To make the focussing magnetic field in a deflection beam drift space almost parallel to a tube axis, a focussing magnetic field generating coil 32 has the length which completely contains the side end of the second grid for the third grid 4 which becomes a beam starting point to the target 6 which is a beam scanning point. The target 6 of a tube is positioned inside the focussing magnetic field coil 32. Besides, a deflection magnetic field generating coil 32 uses the same deflection center position in the same manner as before. This can improve the beam distortion due to beam deflection, make the picture quality at the target periphery approach to the target center, and obtain comparatively uniform picture quality over all scanning surfaces. |
