A holographic storage demonstration by Optware showed a digital movie being played from an optical disk (an HVD or Holographic Versatile Disk), on which it had been stored using a holographic technique. Why bother?
The technique could store 1TB of data on a disk similar in size to a single layer DVD; that's 200 times more data. The transfer speed is 1GB/sedc, which is 40 times faster than the DVD. Using a conventional optical disc as the base makes mass-market manufacturing and pricing practicable goals.
Optware has developed a Colinear Holographic data storage system which co-exists with the pit-based recording and reflective layer servo tracking systems of conventional CDS and DVDs. The pre-formatted pits have, until now, generayed light diffusion 'noise' during read and write operations. This deleteriously affects the light signal quality used in holographic read and write operations, rendering conventional optical disk use un-fesible - until now.
Optware has added a 'dichroic mirror' layer between the recording and reflerctive layers of the disk.
This cuts out or blocks the noise generated by the pits and ensures higher and usable holographic signal data during read and write operations. A dichroic mirror is a mirror, obviously, that selectively reflects light according to its wavelength, its colour. Thus it could reflect visbile light but let infrared (IR) radiation through, or vice-versa.
So-called hot mirrors, which reflect IR but pass visible light, are commonly used in digital cameras to prevent infrared energy from affecting the image. Other dichroic mirrors, which reflect visible light but pass IR, are commonly used in slide projectors to protect the slides from the intense heat generated by the lamp.
Optware uses its mirror to block the light diffusion caused by the address pits.
The holographic data is stored as 'laser interference fringes'. Techworld has described holographic data storage here. Optware now joins InPhase Technologies and Aprilis as potential holographic storage suppliers.
Optware's demonstration shows the highest holographic storage capacity and transfer rate we have come across so far. It's use with a video application could be clever as it could help attract investment money to help commercialise the technology.
The company says more "technical details will be presented at "COST Action P8 (Cooperation in the field of Scientific and Technical Research, which will be held in Paris on September 16 and 17." If the company achieves a commercially viable 1TB HVD then the way would be clear for many holographic storage applications. Such performance would look tempting for storage of ordinary data and not just video. However just 200GB capacity is expected in the first stage development. A write-once disk is expected first with a re-writable disk following on.
The collinear holography technique
This is, according to Optware, "a patented technology originally proposed by Optware founder and chief evangelist Hideyoshi Horimai. It combines a reference laser and signal laser on a single beam, creating a three-dimensional hologram composed of data fringes. This image is illuminated on the medium using a single objective. Using this breakthrough mechanism, Optware dramatically simplified and downsized the previously bulky and complicated systems required to generate holograms. Further enhancements were achieved with Optware's exclusive servo system. The introduction of this mechanism enabled reduced pickup size, elimination of vibration isolators, high-level compatibility with DVD and CD discs and low-cost operation, effectively obliterating the remaining obstacles to full commercialization."
More on the technology can be found here.
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