PURPOSE: When moving a magnetic field regulating mechanism in the direction where the focus fiedl will be stronger, to prevent the deterioration of the temperature variation compensating characteristic even when the field strength is varied, by making such that the ratio between volume and the surface area at the portion of a temperature variation compensating mechanism which isn't lapped over the field regulating mechanism will decrease gradually.
CONSTITUTION: A temperature variaton compensating mechanism 6 made of uniform magnetic steel is fixed to the outercircumference of a permanent magnet 2 or a magnetic field generating means, while a tubular fiedl regulating mechanism 5 made of soft ferromagnetic material is located movably in axial direction against the next section 1 of a cathode ray tube bulb. Consequently when said mechanism 5 will move in the direction where the focus field will be stronger, the ratio between the volume and the surface area at the portion of the compensating mechanism which lapped over the regulating mechanism 5 will decrease gradually. In other word the flux amount shunted to the mechanism 5 in accordance to the movement is reduced, while the flux amount passing at the non-overlap section is also reduced thereby the thickness of the uniform magnetic steel is made thin. Consenquently the temperature variation compensating characteristic will not deteriorate even if the field strength is varied.
SAKURAI SOUICHI
OSAKABE KUNIHARU
INOUE FUMIO
