Videocolor

Videocolor, S.a.

Bruno Roussel

Alain Dumesnil

Didier Thibaudin

Laurent Jourdheuil

A deflection yoke includes a first core portion and a core extension portion. The core extension portion is located in the rear of the yoke closer to the beam entrance region. To adjust the yoke for the particular cathode ray tube on which it is mounted, the position of the yoke is adjusted for obtaining acceptable image geometry. Then, the core extension is moved with respect to the first core portion in a direction perpendicular to the longitudinal axis of the tube to obtain convergence symmetry while the position of the first core portion remains the same. In this way, convergence symmetry adjustment is accomplished separately from image geometry adjustment.

Deflection yoke with a core extension

A main deflection device of a cathode ray tube generates a main deflection field to deflect an electron beam on the screen of the tube. An auxiliary deflection device located between the main deflection device and the envelope of the tube generates a corrective deflection field to correct geometry errors, for example. The auxiliary deflection device includes a ring core that has a plurality of inwardly pointing projections along the ring and a plurality of associated coils that generate the corrective field. A plurality of adjustable impedances parallels the coils.

Geometry corrector for a cathode ray tube

A deflection coil system for a picture tube has a primary deflection coil and an auxiliary deflection coil. The primary and auxiliary deflection coils are each operable to produce a respective magnetic field having a first polarity within a region defined by the coil and an opposite polarity in a second region. Each of the two coils is arranged such that part of the positive polarity field of each coil and all of its opposite polarity field, are in each case coupled to the other coil. This cancels the effects of cross coupling of the primary and auxiliary deflection coils, which are placed in proximity to each other on the same axis, for example on the neck and envelope of a television display tube. At least one of the primary and auxiliary deflection coils may be a saddle shaped deflection coil and has a flat end turn section, substantially defining the opposite polarity area. The primary and auxiliary deflection coils are overlapped on the tube over at least part of this end turn section.

Deflection yoke arrangement with overlapping deflection coils

The deflecting yoke for a cathode-ray tube of the invention includes a magnetic circuit enveloping the back flares of the deflecting coils, which are folded down into the extension of the central parts of these coils. The end of the back part of the magnetic circuit extends radially inwards until it substantially makes contact with a neck portion of the cathode-ray tube.

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Genlis, France

Bruno Roussel