The fundamental components of a holographic storage systems are shown in the
figure at right.
The device first splits a blue argon laser beam into seperate reference and object beams. The object beam that carries the information, gets expanded so that it fully illuminates a spatial light modulator (SLM). An SLM is simply an LCD panel that displays a page of raw binary data as an array of clear or dark pixels.
To read the stored data, the hologram is illuminated with the reference beam. Each page of the hologram is recorded seperately. To record on the hologram, the data in the form of electric signal is converted to optical signals by a page composer. The controller generates the address to access the desired page. This results in the exposure of a small area of the recording medium through an aperture. The optical output signal is directed to the exposed area by the deflector. Using this beam deflecting mechanism, the light (which carries the information) and the reference beam are made to interact. The interference paatern is thus recorded on the hologram. To record a different page, the aperture is moved and the above process is repeated.
For data retrieval, the laser (reference beam) is focused on the appropriate page according to the address generated. A photo detector array on the other side of the hologram records the image of that sub-hologram.