<ul><li>Holographic memory is a technology that can store information at high density inside crystals or photopolymers . </li></ul><ul><li>The advantage of this type of data storage is that the volume of the recording media is used instead of just the surface . </li></ul>
Technical aspects <ul><li>Like other media, holographic media is divided into write once and rewritable media . </li></ul><ul><li>Rewritable holographic storage can be achieved via the photorefractive effect in crystals </li></ul>
<ul><li>Mutually coherent light from two sources creates an interference pattern in the media. These two sources are called the reference beam and the signal beam </li></ul>
<ul><ul><li>To record on the hologram, the data in the form of electric signal is converted to optical signals by a page composer </li></ul></ul><ul><li>The controller generates the address to access the desired page </li></ul><ul><li>This results in the exposure of a small area of the recording medium through an aperture </li></ul>
<ul><li>The optical output signal is directed to the exposed area by the deflector </li></ul><ul><li>Using this beam deflecting mechanism, the light (which carries the information) and the reference beam are made to interact </li></ul>
<ul><li>The interference pattern is thus recorded on the hologram. To record a different page, the aperture is moved and the above process is repeated. </li></ul>
<ul><li>To retrieve the information stored in a hologram, shine the reference beam directly onto the hologram. When it reflects off the hologram, it holds the light pattern of the image stored there. Then send this reconstruction beam to a CMOS sensor to recreate the original image. </li></ul>
ADVANTAGES <ul><li>HVD offers several advantages over traditional storage technology. HVDs can ultimately store more than 2 terabyte (TB) of information -- that's 400 times more than a single-sided DVD and 40 times more than a current double-sided Blu-ray than a single-sided DVD and 20 times more than a current double-sided Blu-ray DVD </li></ul>
<ul><li>HVDs also use a thicker recording layer than DVDs -- an HVD stores information in almost the entire volume of the disc, instead of just a single, thin layer. </li></ul><ul><li>HVDs storing holograms in overlapping patterns , while a DVD basically stores bits of information side-by-side </li></ul>
<ul><li>The other major boost over conventional memory systems is HVD's transfer rate of up to 1 gigabyte (GB) per second -- that's 40 times faster than DVD. An HVD stores and retrieves an entire page of data, approximately 60,000 bits of information, in one pulse of light, while a DVD stores and retrieves one bit of data in one pulse of light. </li></ul>
Development and marketing <ul><li>At the National Association of Broadcasters 2005 (NAB) convention in Las Vegas, conducted the first public demonstrations of the world’s first prototype of a commercial storage device at the Maxell Corporation of America booth. </li></ul>
<ul><li>The three main companies involved in developing holographic memory, Polaroid spinoff Aprilis, and Optware of Japan ,IBM </li></ul>
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