Cathode ray tube having an electron gun

A cathode ray tube having an electron gun, the electron gun being oriented along an axis of the electron gun, the electron gun comprising at least one first quadrupolar device which comprises a first electrode, a second electrode and a third electrode that are disposed in parallel and in series along the axis of the gun, the first electrode, the second electrode and the third electrode being of plane form and each electrode possessing a central aperture, a right lateral aperture and a left lateral aperture, all three being substantially rectangular, the large sides of the apertures of the first and of the third electrode being oriented along a first direction while the large sides of the apertures of the second electrode being oriented along a second direction orthogonal to the first direction;

• each aperture possessing a centre, the centres of the central apertures of the three electrodes being aligned along the axis of the gun, the centres of the left and right lateral apertures of the second electrode being situated along respectively a first axis and a second axis that are parallel to the axis of the gun, the centres of the left lateral apertures of the first electrode being situated on a third axis parallel to the axis of the gun, the centres of the right lateral apertures of the first electrode being situated on a fourth axis parallel to the axis of the gun, the centre of the left aperture of the third electrode is situated on a fifth axis parallel to the axis of the gun, while the centre of the right aperture of the third electrode is situated on a sixth axis parallel to the axis of the gun, wherein:
• the third, fifth or both the third and fifth axes are distinct from the first axis and the fourth, sixth or both the fourth and sixth axes are distinct from the second axis,
• the first, third and fifth axes are symmetric respectively with the second, fourth and sixth axes with respect to the axis of the gun,
• the apertures possess holes or widenings allowing the alignment of the electrodes, the holes or widenings for aligning the left lateral apertures of the three electrodes being situated along the first axis, likewise, the holes or widenings for aligning the right lateral apertures of the three electrodes being situated along the second axis, and,
• the holes or widenings are situated on the large sides of the apertures of the electrodes and are of circular shapes whose radius R is equal to R=(H/2)/cos(αΠ/2) with H being the distance between the two large sides of an aperture and α being the percentage of the perimeter of the circle of radius R.