Magnetic focusing device.

摘要

A magnetic focusing device (20) for a cathode ray tube comprises a plurality of substantially cylindrical permanent magnets (1), each having a longitudinal axis. A holder (3) positions the magnets in an annular array at substantially equally spaced intervals in which the axes are substantially parallel to one another. Annular flanges (2) of high magnetic permeability are disposed over longitudinally opposite ends of the magnets. First (5) and second (6) annular windings are symmetrically disposed substantially adjacent to and inwardly from the array of magnets. The magnetic mass of the focusing device can be varied by changing the number of magnets and/or the length of the magnets in the array. The magnets are magnetized in situ in the array by energizing a winding (4) common to each of the magnets, after which the common winding is removed. <IMAGE>