Picture display device with core means comprising compensation coils

Details

Inventors: Sluyterman, Albertus A. S.;
Assignee: U.S. Philips Corporation (New York, NY)
Primary Examiner: Pascal; Robert J.
Assistant Examiner:
Attorney, Agent or Firm:

Picture display device comprising a display tube, a deflection unit and a compensation coil system for generating a magnetic compensation field which is oppositely directed to the line frequency radiation field of the deflection unit in a space in front of the display screen. The compensation coil system comprises two coils each being wound on a rod-shaped core portion. The core portions are arranged in a V-formation in the y-z plane, symmetrically relative to the x-z plane. Alternatively, the compensation coil system may comprise two pairs of coils arranged in this way and located in planes parallel to the x-y plane and equidistantly therefrom.

DETAILED DESCRIPTION It is the object of the invention to provide compensation of the radiation field of the line deflection coil with less energy and less sensitivity than is realized by the known measures.
The invention has a compensation coil system on the screen-sided end of the deflection unit and which includes at least one pair of core means, each core means comprising a rod-shaped magnetic core portion provided with a coil and extending in a plane whose normal is transverse to the longitudinal axis of the display tube, said core means being positioned symmetrically about a plane of symmetry and symmetrically with respect to a plane which including the longitudinal tube axis and which is transverse to the plane of symmetry, the longitudinal axes of co-planar core means intersecting the plane of symmetry at substantially the same, retrograde point at an acute angle of 90.
degree.
-.
phi.
, and the centers of the core means of each pair being situated between the center of the deflection unit and the display screen.
The simplicity of this solution for radiation compensation, which is based on the use of rod-shaped core means of a magnetizable material provided with toroidal compensation coils, is superior to all known solutions based on the use of coreless, i.
e.
air-cored coils.
A coil surrounding a core of a magnetizable material occupies little space and its loss of sensitivity is small.
Within the scope of the invention the compensation coil system may comprise a first pair of core means extending in a first plane whose normal is transverse to the tube axis, and a second pair of core means extending in a second plane whose normal is transverse to the tube axis, said first and second planes being located equidistantly from the tube axis.
A configuration which was tested was found to compensate the line deflection stray field effectively, while there was less loss of deflection sensitivity (for example, 5 times less) times less) than in the known compensation coil systems.
An embodiment which provides even more advantages is characterized in that the compensation coil system comprises one pair of core means extending in a plane which comprises the tube axis and which is transverse to the plane of symmetry of the line deflection coils

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