Color display device having quadrupole convergence coils

A color display device comprising

• an in-line electron gun (5) for generating three electron beams (6,7,8) located substantially within a plane extending in an X-direction of a rectangular X-Z coordinate system,
• deflecting means (51) for deflecting the electron beams (6,7,8), and
• convergence means (14′) for dynamically influencing the convergence of the electron beams, the convergence means (14′) comprising means for generating a magnetic field that corresponds to a magnetic quadrupole field, said means for generating comprising a ring-shaped element (21′) having coils (22′) that comprise electrically conductive wires which have been toroidally wound in a winding direction and according to a winding density distribution N (φ) given by N (φ)=N0 cos (2φ)+C;
• where φ is an angle enclosed by the X-direction and a line between an element of the coil and the center of the coil, which ranges between 0° and 360°, N0 is a given winding density, the sign of N (φ) denotes the winding direction, and C is a constant,
• wherein said ring-shaped element (21′) comprises two parts (60,68), a first part (60) being positioned closer to the in-line electron gun (5) than a second part (68), at least one of said parts having the coils (22′).

A method of manufacturing a convergence unit (14′) for dynamically influencing a convergence of electron beams in a color display device (1), the convergence unit (14′) comprising a ring-shaped element (21′) having coils (22′),

• said method comprising the steps of:
• providing the ring-shaped element (21′),
• winding an electrically conductive wire toroidally around the ring-shaped element (21′) in a winding direction and according to a winding density distribution N (φ) given by N (φ)=N0 cos (2φ)+C;
• where φ is an angle enclosed by the X-direction and a line between an element of the coil and the center, which ranges between 0° and 360°, N0 is a given winding density,.the sign of N (φ) denotes the winding direction, and C is a constant unequal to zero.