Abstract: A device for shielding the earth magnetic field permeating through a neck of a cathode ray tube (CRT) to improve purity, raster and convergence characteristics in the CRT. The device for shielding the earth magnetic field according to the present invention includes a tube type shielding device, the device made of a material having a high magnetic permeability and low coercive force, and the device having four evenly spaced extension parts formed on the periphery thereof along the CRT axis. The device is made of a Ni—Fe permalloy including Ni of more than 50 weight %, preferably about 78.5 weight %. The device has an inner diameter capable of mounting on the outer surface of the neck. Alternatively, the device may be mounted on the neck by means of a both-sided adhesive tape. The device may be also securely mounted on the neck by means of a thermal contraction tube.

Abstract: A convergence magnet assembly for a cathode ray tube (CRT) includes a convergence magnet assembly having at least a one pair of magnet rings having magnetized portions at angular intervals and installed on a neck portion of a CRT for static convergence of three electron beams in an in-line arrangement; and a correction ring with an odd number of poles located at one side of the neck, adjacent an electron beam at one side of the in-line three electron beams, increasing a shift in the electron beam position caused by the pair of magnet rings.