hollographic versetail disc

Abstract:

An HVD (holographic Versatile Disc), a holographic storage media, is an advancedoptical disc that’s presently in the development stage. Polaroid scientist J. vanHeerden was the first to come up with the idea for holographic three-dimensionalstorage media in 1960. An HVD would be a successor to today’s Blu-ray and HD-DVD technologies. It can transfer data at the rate of 1 Gigabit per second. Thetechnology permits over 10 kilobits of data to be written and read in parallel with asingle flash. The disc will store upto 3.9 terabyte (TB) of data on a single optical disk.Holographic data storage, a potential next generation storage technology, offers bothhigh storage density and fast readout rate. In this article, I discuss the physical originof these attractive technology features and the components and engineering requiredto realize them. I conclude by describing the current state of holographic storageresearch and development efforts in the context of ongoing improvement toestablished storage technologies.


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Hvd(Holographic Versatile Disc)

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HVD report


What is Holographic Versatile Disc (HVD)?

Holographic Versatile Disc (HVD) is an optical disc technology, which would greatly increase storage over
Blu-ray Disc and HD DVD optical disc systems. It employs a technique known as collinear holography, whereby two lasers, one red and one blue-green, are collimated in a single beam. The blue-green laser reads data encoded as laser interference fringes from a holographic layer at the top of the disc while the red laser is used as the reference beam and to read servo information from a regular CD style aluminium layer near the bottom. Servo information near is used to monitor the position of the read head over the disc, similar
to the head, track, and sector information on a conventional hard disk drive. A dichroic mirror layer fitted between the holographic data and the servo data reflects the blue-green laser while letting the red laser pass
through. This prevents interference from refraction of the blue-green laser off the servo data pits and is an advance over past holographic storage media, which either experienced too much interference, or lacked the
servo data entirely, making them incompatible with current CD and DVD drive technology. Here discs have the capacity to hold up to 3.9 terabytes (TB) of  information, which is approximately 6,000 times the capacity of a CD-ROM, 830 times the capacity of a DVD, 160 times the capacity of single layer Blue-ray Discs, and about 12 times the capacity of standard computer hard drives as of 2007. The HVD also has a transfer rate of 1 gigabits.

Holographic Versatile Disc structure

Green writing/reading laser
Red positioning/addressing laser
Hologram (data)
Polycarbonate layer
Photo polymeric layer
Distance layers
Dichroic layer
Aluminium reflective l


How Holographic Versatile Discs Work ?

Holographic memory technology is not new. Developers have offered the improved storage capacity of this method that surpasses CD and DVD storage limits. Not only that, movement of data is much quicker and more efficient. The holographic method transfers data 40 times faster than the best DVD. Yet holographic versatile discs have yet to become the standard in commercial electronics. Why? Cost is one key factor. The complexity of establishing and using a complete system is another limitation.

Holography is at the heart of this unique memory-storage method. Holography records patterns of light and produces an object in three dimensions. This visible image is known by the name “hologram.” Holography wouldn’t be possible without a laser light beam split into a reference beam and the information beam. This latter beam passes through an image and takes the information about that image in light waves. When the two beams meet there is light interference at the intersection. This is recorded on a photosensitive disc.


Accessing this information means directing the beam to the hologram. The light pattern is retrieved and can be recreated elsewhere. The major difference between recreating a visible hologram is that in memory storage the holographic information is stored in digital form. The light and dark areas correspond to 1s and 0s in binary/digital method. This method can increase the amount of data stored from several gigabytes to 1 terabyte or more. Most detailed information about the holographic versatile disc indicates that the recording layer is thicker than on a DVD, for example.

One of the technical problems in making holographic versatile disc systems affordable lies with the complex systems necessary to get the laser beams aligned for accuracy. For this technology to work well the beams of light must intersect perfectly. Currently, the two beams are directed toward the image at different angles. Newer experimental technology focuses on sending the two beams on the same line, which means they strike the recording layer at the same angle.

Developers also struggle with the fact that the equipment and the discs will probably have to be proprietary, meaning that they won’t work with current technology.