Holographic Versatile Disc (HVD) is an optical disc technology which would hold up to 3.9 terabytes (TB) of information. It employs a technique known as collinear holography, whereby two lasers, one red and one green, are collimated in a single beam. The green laser reads data encoded as laser interference fringes from a holographic layer near 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 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. On a CD or DVD this servo information is interspersed amongst the data.
A dichroic mirror layer between the holographic data and the servo data reflects the green laser while letting the red laser pass through. This prevents interference from refraction of the 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.[1] These discs have the capacity to hold up to 3.9 terabytes (TB) of information, which is approximately 5,500 times the capacity of a CD-ROM, 830 times the capacity of a DVD, 160 times the capacity of single-layer Blu-ray Discs, and about 7 times the capacity of standard computer hard drives as of 2007. The HVD also has a transfer rate of 1 Gbit/s (128 MB/s). Optware was expected to release a 200 GB disc in early June 2006, and Maxell in September 2006 with a capacity of 300 GB and transfer rate of 20 MB/s.[2] Since the announcement, there have been no further news or products on market.
A dichroic mirror layer between the holographic data and the servo data reflects the green laser while letting the red laser pass through. This prevents interference from refraction of the 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.[1] These discs have the capacity to hold up to 3.9 terabytes (TB) of information, which is approximately 5,500 times the capacity of a CD-ROM, 830 times the capacity of a DVD, 160 times the capacity of single-layer Blu-ray Discs, and about 7 times the capacity of standard computer hard drives as of 2007. The HVD also has a transfer rate of 1 Gbit/s (128 MB/s). Optware was expected to release a 200 GB disc in early June 2006, and Maxell in September 2006 with a capacity of 300 GB and transfer rate of 20 MB/s.[2] Since the announcement, there have been no further news or products on market.
Technology
Current optical storage saves one bit per pulse, and the HVD alliance hopes to improve this efficiency with capabilities of around 60,000 bits per pulse in an inverted, truncated cone shape that has a 200 micrometer diameter at the bottom and a 500 micrometer diameter at the top. High densities are possible by moving these closer on the tracks: 100 GB at 18 micrometers separation, 200 GB at 13 micrometers, 500 GB at 8 micrometers and a demonstrated maximum of 3.9 TB for 3 micrometer separation on a 12 cm disc.
The system uses a green laser, with an output power of 1 watt, a high power for a consumer device laser. So a major challenge of the project for widespread consumer markets is to either improve the sensitivity of the polymer used, or develop and commoditize a laser capable of higher power output and suitable for a consumer unit
Current optical storage saves one bit per pulse, and the HVD alliance hopes to improve this efficiency with capabilities of around 60,000 bits per pulse in an inverted, truncated cone shape that has a 200 micrometer diameter at the bottom and a 500 micrometer diameter at the top. High densities are possible by moving these closer on the tracks: 100 GB at 18 micrometers separation, 200 GB at 13 micrometers, 500 GB at 8 micrometers and a demonstrated maximum of 3.9 TB for 3 micrometer separation on a 12 cm disc.
The system uses a green laser, with an output power of 1 watt, a high power for a consumer device laser. So a major challenge of the project for widespread consumer markets is to either improve the sensitivity of the polymer used, or develop and commoditize a laser capable of higher power output and suitable for a consumer unit
Storage capacity in context
Holographic Versatile Card, a variation of the Holographic Versatile Disc
It has been estimated that the books in the U.S. Library of Congress, one of the largest libraries in the world, would contain a total of about 20 terabytes if scanned in text format. Not including images from the books, the content could be stored with capacity to spare on six 3.9 TB discs.
At 15 meter resolution and 32-bit color (about the resolution found in unpopulated areas on Google Earth), a map of the land masses of Earth would occupy just over 2 TB.
Using MPEG4 ASP encoding, a 3.9 TB HVD could hold 4,600–11,900 hours of video—just over one year of uninterrupted video at usual encoding rates.[3]
Using typical satellite radio encoding (CT-aacPlus at 40 kbit/s), a 3.9 TB HVD could hold over 26.5 years of uninterrupted stereo audio.
Holographic Versatile Card, a variation of the Holographic Versatile Disc
It has been estimated that the books in the U.S. Library of Congress, one of the largest libraries in the world, would contain a total of about 20 terabytes if scanned in text format. Not including images from the books, the content could be stored with capacity to spare on six 3.9 TB discs.
At 15 meter resolution and 32-bit color (about the resolution found in unpopulated areas on Google Earth), a map of the land masses of Earth would occupy just over 2 TB.
Using MPEG4 ASP encoding, a 3.9 TB HVD could hold 4,600–11,900 hours of video—just over one year of uninterrupted video at usual encoding rates.[3]
Using typical satellite radio encoding (CT-aacPlus at 40 kbit/s), a 3.9 TB HVD could hold over 26.5 years of uninterrupted stereo audio.
Competing technologies
HVD is not the only technology in next-generation, high-capacity optical storage media. InPhase Technologies is developing a rival holographic format called Tapestry Media, which they claim will eventually store 1.6 TB with a data transfer rate of 120 MB/s (960 Mbit), and several companies are developing TB-level discs based on 3D optical data storage technology. Such large optical storage capacities compete favorably with both HD DVD and Blu-ray Disc. However, holographic drives are projected to initially cost around US$15,000, and a single disc around US$120–180, although prices are expected to fall steadily.[4] The market for this format is not initially the common consumer, but enterprises with very large storage needs
