Display having particular polarisation modifying layer

A display is provided for providing a restricted viewing mode, for example a private viewing mode where the display may be viewed from a limited region of space by a single viewer and not by other people outside the viewing region. The display comprises a source of polarised light and an output polariser. Between these are provided a controllable pixellated spatial polarisation modulating layer, for example of the liquid crystal type. Also, a polarisation modifying layer is provided between the polarisers and is spaced from the modulating layer. The modifying later comprises a plurality of sets of regions with the regions of each set having the same polarisation modifying effect and the regions of different sets having different polarisation modifying effects. The light path between the modulating layer and the modifying layer is polariser-free. A controller supplies modified image data to compensate for the effect of each region through which light from one or more associated pixels passes to the viewing region so that a viewer in the viewing region sees the displayed image. Outside the viewing region, light passes through regions for which the pixels receive uncompensated data so that the image is obscured or corrupted and is not visible. The modifying layer may be disablable in order to provide a public viewing mode for viewers throughout a wide viewing region.