An optical element (22) comprises a material (27) thermally switchable between a first
stable state and a second
stable state different from the first state and a switching mechanism (28a-28c) for switching one or more selected areas of the material (27) between the first state and the second state thereby to change the transmissivity of one or more selected areas of the optical element (22). The optical element may be placed in an
optical path through another component such as, for example, a display (21), reflector or backlight, such that the optical element may be controlled to change the optical properties of the component. The properties that may be changed include, but are not limited to, the display mode of a display (21), viewing angle range, brightness / luminance, and colour. For example, if the element is substantially non-transmissive for one state of the thermally switchable material, the thermally switchable material may be arranged to provide a
parallax barrier, in one state. Thus a display (21) may be switched between a directional display mode, for example a 3D-mode or multi-view display mode, and a conventional 2-D display mode by putting the thermally switchable material into its appropriate state—when the thermally switchable material is put into the non-transmissive state the
parallax barrier is enabled, and when the thermally switchable is put into another state the
parallax barrier is disabled.