GB749024A - Improvements in or relating to deflection systems for cathode ray tubes - Google Patents

Abstract

749,024. Cathode-ray tubes. COMPAGNIE POUR LA FABRICATION DES COMPTEURS ET MATERIEL D'USINES A GAZ. Sept. 29, 1953 [Sept. 29,1952], No. 26727/53. Class 39 (1). A magnetic deflecting system produces a spiral distortion of the scanned field which can be used to correct for a spiral distortion already existing elsewhere in the tube. The distortion is produced by arranging that (a) the direction of the mean magnetic field rotates progressively about the beam axis from the entry to the exit of the system, so that the main plane of deflection of the exit beam is not perpendicular to the mean magnetic field at the exit; and (b) that the exit field is non-uniform away from the axis so that the forces perpendicular to the main plane of deflection generated by a condition (a) are non-uniform to give the spiral distortion. In one form the ends 12, 13 and 14, 15, Fig. 5, of the coils are twisted with respect to one another as shown to give the screw field; the windings may be sunk in skewed slots in a magnetic armature and distributed to give a desired law. In another form a toroidal magnetic core is wound with skewed coils, Fig. 7 (not shown); and these may be further skewed radially so that the inner turns of the coils are advanced circumferentially with respect to the outer ones, Fig. 8 (not shown). Applications are described to (1) an image iconoscope in which spiral distortion is produced in the image section by a non-uniform focusing coil; (2) a television receiver tube where the focusing and deflecting systems interfere to give spiral distortion.