U.S. Philips Corporation

Robert H Fastenau

Jacob Koorneef

Aart A Van Gorkum

Johannes T Klomp

Martinus H Van Den Broek

Johannes T Van Roosmalen

Paulus J Van Der Heijden

Matthijs J Baan Hofman

A method of manufacturing a color display tube having a magnetic quadrupole post-focusing mask, in which the mask is magnetized by magnetic field shaping means of soft iron, or the magnetic equivalent, having raised portions, for example strips placed against opposite sides of the mask sheet and subjected to an external strong magnetic field by an electromagnet to induce magnetic poles through the thickness of the mask sheet. The geometric arrangement of the raised portions of the field shaping means is such that cyclically a north pole, a south pole, a north pole and a south pole are induced into the sheet material surrounding each aperture. Using this technique, the entire area of a mask sheet can be magnetized in one operation. Also masks for small tubes and high definition tubes can be made.

Method of manufacturing a color display tube having a magnetic

A monochrome cathode ray tube having an electromagnetic deflection unit (9) and a directly adjoining integrated focusing multipole correction unit (10) which serves both to generate a static focusing field and to generate higher order multipole correction fields to correct for spot distortion errors. In particular quadrupole fields are generated to correct for astigmatism errors.

Cathode ray tube having a magnetic focusing lens

In a method of manufacturing a color cathode-ray tube comprising a magnetic quadrupole post-focusing mask (7) the mask (7) is formed by a plate of permanent magnetizable material in which apertures (9) are provided arranged according to rows. Sections of the plate are successively magnetized by positioning parallel conductors (21, 22, 23) on at least one side of the plate in such manner that each time two conductors through which an electric current flows in opposite directions are situated between two rows of apertures (9) and a magnetic quadrupole is formed along the circumference of each of the apertures (9). A number of outermost conductors (30, 31, 32, 33) determines an edge area of the section. In order to prevent the occurrence of disturbing magnetization errors in the edge area, the edge area is made to coincide with a part of a preceding section already magnetized according to the desired strength. A magnetic induction is generated in the edge area according to a pattern corresponding to the existing pattern in the preceding section but having a strength which decreases towards the outermost conductor (30 ).

Method of manufacturing a color cathode-ray tube comprising a magnetic

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Eindhoven, Netherlands

Robert H Fastenau