A video display device is provided to achieve local control for a high-quality 3D image while reducing extraneous radiation. A slider slides along the first and second elongate closure members to engage or to separate the first and second elongate closure members. The first electrodeionization operation is performed at a voltage calculated to remove strongly ionized species such as calcium and magnesium from the feed water without scaling. The apparatus comprises control means for controlling means for displacement of the turret in a plane perpendicular to the first axis and suitable for displacing the turret in said plane when the turret is driven in rotation about the first axis during the sensing of the mount.