HOLOGRAPHIC IMAGE DISPLAY SYSTEMS

This invention relates to holographic image display systems. We describe an optical module for a holographic image projection system which displays a hologram (204) of a low spatial frequency portion of input image data on an SLM (SLM1) to form a holographically-generated intermediate real image which is in turn modulated (SLM2) by a higher spatial frequency portion of the image data (206), to display the image. The optical module comprises: at least one laser light source; a first spatial light modulator (SLM1) to modulate light from said at least one laser light source; intermediate optics (L4) to provide an intermediate real image plane at which a real image produced by a hologram on said first SLM is formed; a second SLM (SLM2) located at said intermediate real image plane to intensity modulate said real image; and output optics (L5,L6) to project an image of said intensity modulated real image; and wherein a resolution of said second SLM is greater than a resolution of said first SLM.