Holographic Versatile Disc

Holographic Versatile Disc (HVD) is an optical disc technology that 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 aluminum 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. These discs have the capacity to hold up to 3.9 terabytes (TB) of information, which is approximately 5,800 times the capacity of a CD-ROM, 850 times the capacity of a DVD, 160 times the capacity of single-layer Blu-ray Discs, and about 4 times the capacity of the largest computer hard drives as of 2007. The HVD also has a transfer rate of 1 Gbit/s (125 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. On June 28 , 2007, HVD standards have been approved and published.
HVD is not the only technology in 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, and several companies are developing TB-level discs based on 3D optical data storage technology. Such large optical storage capacities compete favorably with the Blu-ray Disc format. 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. The market for this format is not initially the common consumer, but enterprises with very large storage needs.