As the need for increased dam storage changes, the search for higher density, faster access memory technologies also increases. One of these, holographic data storage, provides the promise for increased access to higher density data. The techniques for realizing such storage typically utilize some type of storage media, such as photorefractive crystals or photopolymer layers, to store 3-D "stacks" of data in the form of pages of data. Typically, coherent light beams from lasers are utilized to perform the addressing, writing and reading of the data from the storage media by directing these beams at a specific region on the surface of the media. Writing is achieved by remembering the interference pattern formed by these beams at this region. Reading is achieved by detecting a reconstructed light beam as it exits the storage medium, the data then being extracted therefrom. Addressing is achieved by the positioning of the laser beams, and this is typically done through the mechanical movement of mirrors or lenses; however, the storage media itself can be moved relative to fixed laser beams.
One method for positioning the laser beam onto the storage media is to utilize a fixed optics system that selects a given storage location, such that both the reference beam and the data beam are focused onto the storage location. In order to select another storage location on a two-dimensional holographic media, the storage media can then be moved along its x- and y-axes. Alternatively, the optic system can be more complicated, such that the beams can be located to a particular region without the need to move the media itself. However, apparatus for achieving such movement are quite complex.