a parallax barrier includes a polarization modifying layer having aperture regions , for supplying light of a second polarization when receiving light of a first polarization , separated by barrier regions , for supplying light of a third polarization different from the second polarization when receiving light of the first polarization , and a polarizer selectively operable in a first mode and a second mode . at least one of the aperture regions and the barrier regions alters the polarization of light passing therethrough . the polarizer passes light of the second polarization and blocks light of the third polarization in the first mode and passes light of the third polarization in the second mode .