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InPhase Announces 300GB Holographic Discs
turboflux writes "After rolling out prototype holographic drives last year, ExtremeTech reports that InPhase has announced they intend to ship drives to commercial customers in 2006. InPhase originally intended on shipping the 200GB version of their media this year. Another article on Engadget mentions that 1TB discs will be available in 2009."
that seems kind low
That is because
Second-generation rewriteable products are due in 2007 or 2008, Murphy said
Releasing 1.5 TB disks would satisfy the storage market immediately. They first get people interested in the 'low density' variant, then those people will become greedy again for the higher density versions in 2007 or 2008.
Stachel
It's sort of the same, but then again not really. From InPhase's website:
Light from a single laser beam is split into two beams, the signal beam (which carries the data) and the reference beam. The hologram is formed where these two beams intersect in the recording medium.
The process for encoding data onto the signal beam is accomplished by a device called a spatial light modulator (SLM). The SLM translates the electronic data of 0's and 1's into an optical "checkerboard" pattern of light and dark pixels. The data is arranged in an array or page of around a million bits. The exact number of bits is determined by the pixel count of the SLM.
At the point of intersection of the reference beam and the data carrying signal beam, the hologram is recorded in the light sensitive storage medium. A chemical reaction occurs in the medium when the bright elements of the signal beam intersect the reference beam, causing the hologram stored. By varying the reference beam angle, wavelength, or media position many different holograms can be recorded in the same volume of material.
"This does not seem to be holographic in the sense we are expecting."
What sense were you expecting? A normal holographic image does precisely that, chemical reactions induced by light, it's the same basic principle as normal photography. The difference is that you use lasers (coherent phase background), and increase resolution to the point that you can store not just amplitude but relative phase information of the wavefront.
The full wave front of light, including the relative phase is sufficient to recreate the entire wave, including all "3D information". This is known in physics as Huygen's Principle: http://en.wikipedia.org/wiki/Huygens_principle
If the capacity is kind of "low" by holographic memory standards, it might be because this medium doesn't use any other kind of multiplexing beside spatial multiplexing.
Basically, what we have here is a disc with several "holographic bits", scattered across the disc just like a regular compact disc. The main difference here is that when you read an holographic bit with the reconstruction beam, you get a full page of data (here, a 1024x1024 image - hence 1 Mbit).
What is interesting with holographic memory is that when you use thick layers of holographic materials you can also multiplex the data using the angle of the reconstruction beam, or its wavelength. That means that you can hit the same area on the disc with the reconstruction beam at a different angle, and get a different page of data. Or use a different laser beam, and get again another page of data.
Of course, this process seriously complexifies the hardware that must be used to read an hoographic medium, but it is the key to reach tremendous densities with the holographic technique.