there is provided a projection display device comprising : a light source , an sbg device comprising a multiplicity of separately sbg elements sandwich between transparent substrate to which transparent electrodes have been applied . the substrates function as a light guide . a least one transparent electrode comprises plurality of independently switchable transparent electrodes elements , each electrode element substantially overlaying a unique sbg element . each sbg element encodes image information to be projected on an image surface . light coupled into the light guide , undergoes total internal reflection until diffracted out to the light guide by an activated sbg element . the sbg diffracts light out of the light guide to form an image region on an image surface when subjected to an applied voltage via said transparent electrodes .