Method of correcting deflection defocusing in a CRT, a CRT employing same, and an image display system including same CRT

摘要

A method corrects deflection defocusing in a cathode ray tube including an electron gun comprising a plurality of electrodes, an electron beam deflection device and a phosphor screen. This method includes placement of pole pieces of magnetic material in a deflection magnetic field produced by the electron beam deflection device and thereby locally modifies the deflection magnetic field in a path of an electron beam and corrects deflection defocusing of the electron beam corresponding to deflection of the electron beam in amount.