| 摘要 |
PURPOSE:To eliminate the asymmetry of the focusing magnetic field by applying the tetrode magnetic fields for correcting the distribution of magnetization from the outside to collect it after having magnetized a magnetic ring between a cathode of a electron gun and a deflection yoke for focusing an electron beam. CONSTITUTION:A subminiature cathode ray tube used in a viewfinder etc. of a video camara is formed, including an electrostatic focus type electron gun 3, a fluorescent screen 11 not having a metal back, and a magnetic ring 9 provided between a cathode 4 of the electron gun 3 and a deflection yoke 13 and for generating the magnetic field for focusing an electron beam. At the time, after having exhausted the inside of the tube and after having magnetized the magnetic ring 9, the unevenness of distribution of the magnetic field in the magnetic ring 9 is corrected by the use of a device for generating the tetrode magnetic fields which is comprised of the first to the fourth electromagnetic coils 15-16 positioned on the outer peripery of the tube 1, observing a beam spot on the screen 11. Thus, it is possible to carry out the adjustment with high precision and to improve the solution. |
