| 摘要 |
PURPOSE:To prevent a deflecting magnetic field from giving ill influence on the foucsing effect of a main lens by installing a cylinder made of a high permeability material coaxially with an image pickup tube and in an area of a coil bobbin surrounding the electron-beam-focusing part of the image pickup tube and located inside the winding of a deflecting coil. CONSTITUTION:A cylinder 18 made of a high permeability material is installed in an area of a deflecting coil bobbin 15a surrounding an electron-beam-focusing part. As a result, a magnetic field produced by a deflecting coil in an image pickup tube does not encroach upon its main lens and a superior picture quality is obtained despite a shortended total length of the image pickup tube. A slight increase of deflecting electric power is unavodably caused by installing such a shielding cylinder made of a high permeability material. However, it is possible to almost eliminate the difference in the amount of electric power practically by moving the peak of a deflecting magnetic field a little forward by slightly decreasing the total length of the coil. |
