Holographic Versatile Disc
The Holographic Versatile Disc (HVD) is an optical disc technology that was expected to store up to several terabytes of data on an optical disc 10 cm or 12 cm in diameter. Its development commenced in April 2004, but it never arrived due to lack of funding. The company responsible for HVD went bankrupt in 2010. The reduced radius reduces cost and materials used. It employs a technique known as collinear holography, whereby a green and red laser beam 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. A red laser is used as the reference beam to read servoinformation from a regular CD-style aluminium layer near the bottom. Servoinformation 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 servoinformation is interspersed among 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. Standards for 100 GB read-only holographic discs and 200 GB recordable cartridges were published by ECMA in 2007, but no holographic disc product has ever appeared in the market. A number of release dates were announced, all since passed, likely due to high costs of the drives and discs itself, lack of compatibility with existing or new standards, and competition from  video streaming. 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 μm diameter at the bottom and a 500 μm diameter at the top. High densities are possible by moving these closer on the tracks: 100 GB at 18 μm separation, 200 GB at 13 μm, 500 GB at 8 μm, and most demonstrated of 5 TB for 3 μm on a 10 cm disc. The system uses a green laser, with an  output power of 1 watt which is high power for a consumer device laser. Possible solutions include improving the sensitivity of the polymer used, or developing and commoditizing a laser capable of higher power output while being suitable for a consumer unit. Competing technologies. HVD is not the only technology in high-capacity, holographic storage media. InPhase Technologies was developing a rival holographic format called Tapestry Media, which they claimed would 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, in 2006, holographic drives were projected to initially cost around US$15,000, and a single disc around US$120–180, although prices were expected to fall steadily. Since InPhase Technologies was unable to deliver their promised product, they ran out of funds and went bankrupt in 2010. Holography System Development Forum. The Holography System Development Forum (HSD Forum; formerly the HVD Alliance and the HVD FORUM) is a coalition of corporations purposed to provide an industry forum for testing and technical discussion of all aspects of HVD design  and manufacturing. , the following companies are members of the forum: , the following companies are supporting companies of the forum: Standards. On December 9, 2004, at its 88th General Assembly, the standards body Ecma International created Technical Committee 44, dedicated to standardizing HVD formats based on Optware's technology. On June 11, 2007, TC44 published the first two HVD standards: ECMA-377, defining a 200 GB HVD "recordable cartridge" and ECMA-378, defining a 100 GB HVD-ROM disc. Its next stated goals were 30 GB HVD cards and submission of these standards to the International Organization for Standardization for ISO approval. General  Electric. General Electric Global Research Centers created a holographic disc that could hold many times the data of a Blu-Ray — up to 500 GB. As the technology is quite similar to CD, DVD, and Blu-ray technologies, the players were to be cross-compatible with these formats.