Abstract: Apparatus for inducing polarization perception in a human or animal observer. The apparatus may comprise several light emitting diodes (LEDs) (4), an adjacent planar light scattering surface (6), a preferably blue colour filter (88), a sheet polarizer (10), and a liquid crystal cell (LCC) array (12). The absence of a secondary polarizer after the LCC layer means that the polarization state of the light exiting the LCC array (12) is preserved. Each cell of the LCC array (12) can therefore be controlled such that a polarization pattern, e.g. a checkerboard pattern, is produced. The polarization pattern may be temporally variable, e.g. alternating between a sequence of patterns.