Electrically controllable device having variable optical qualities or system which is holographic,thermotropic or which has suspended particles

The invention relates to an element having variable optical properties, comprising (a) a variable light diffusion system which can be electrically controlled, said system being of the optical valve or liquid crystal mode, a suspending particle system or a holographic or thermotropic system (a') which is associated with (b) at least one absorbing element at least within the realm of the visible. The invention can be especially used in the production of overhead projection screens.