Other Types of Optical Storage
Rated: 
Laserdisc
The laserdisc was the first optical storage medium used for commercial purposes, particularly for the movie industry. Paul Gregg invented the laserdisc technology in 1958 (later patented in 1961 and 1969), making use of a transparent disc. More than 1 million households in the United States own Laserdiscs, and although the VHS tape and the DVD format has overtaken the Laserdisc in usage, it has left its mark in America, and more so in Japan. Measuring 12 inches (30 centimeters) in diameter, the Laserdisc is made up of two single-sided discs. Laserdisc is actually an analog format (unlike CDs or DVDs which are digital).
Magneto-optical Disc
Sporting the look of the typical magnetic floppy disc more than the typical optical disc, a magneto-optical disc is made up of ferromagnetic material coated with plastic. To read such a disc, a laser is beamed on the disk and reflects light depending on the magneto-optical Kerr effect. When writing to it, increased intensity of the laser allows for polarization of the electromagnet found on the opposite side of the disc. When the disc cools, the polarized pattern remains. The Sony MiniDisc is also a magneto-optical disc branded mainly for audio purposes. A similar type of disc that also uses both magnetic and optical technologies is the Floptical disc.
Fluorescent Multilayer Disc/Card
Developed by Constellation 3D, this optical storage type uses fluorescent materials, addressing the limitations in the number of layers typical reflective discs have due to interference and scatter, and instead have up to a hundred layers. This means capacities of these discs can reach up to terabytes, even if they're the same size CDs and DVDs are! A related type of fluorescent storage, the fluorescent multilayer card can store up to 10 gigabytes for an area one inch wide.
Digital Multilayer Disc
The DMD or Digital Multilayer Disc is the optical storage technology based on the Fluorescent Multilayer Disc. It was developed by D Data Inc. [link], a company that acquired the patents of Fluorescent Multilayer Disc creators Constellation 3D, after shutting down due to bankruptcy.
Ultra Density Optical
Developed by Plasmon, an Ultra Density Optical (UDO) is an optical disc in a cartridge that can store 30 GB of data, "designed specifically for the secure, long-term storage of high volume document images, emails, customer records, audio or video files, financial information and engineering documentation." [link] Both Write Once, Read Many (WORM) and Rewritable formats are available, and discs with larger capacities are in development (60 and 120 GB versions).
Professional Disc for DATA
Also called ProDATA or PDD, Professional Disc for DATA was first announced by Sony in 2003. With UDO, it was one of the first two optical storage formats to use blue-violet lasers in reading and writing. Its specifications are highly similar to Blu-ray discs and the only difference lies in the capacity (Blu-ray discs can store 25 GB, while PDDs only have 23 GB) and transfer rate (Blu-ray discs use 4.5MB/s, while PDDs have 11 MB/s). As a result, it is much more expensive for the average consumer Blu-ray discs have been targeted at.
Versatile Multilayer Disc
Developed by New Medium Enterprises, Inc. [link], Versatile Multilayer Disc is a high-capacity disc technology that rivals the likes of HD-DVD and Blu-ray discs. While HD-DVD and Blu-ray use blue-violet lasers, which allow for greater capacities per layer, the VMD uses the red laser, which "exploits the unused or wasted space between the existing layers of a standard DVD… without making a drastic shift from red laser technology [to blue-violet lasers]."
Holographic Versatile Disc
Using collinear holography, HVDs use two lasers—red and blue-green ones—to produce a single beam to control reading of the disc. The blue-green laser reads the interference fringes on the holographic layer located at the top of the disc, while the red laser acts as the reference beam reading servo (technology for mechanical control "at a distance"), which monitors information on an aluminum layer at the bottom, particularly the position of the reading head over the disc. This type of optical storage can hold up to 3.9 terabytes and has a transfer rate of 1 gigabyte per second.
Tapestry Media
Also utilizing holographic technology, Tapestry Media are discs 13 cm in diameter (slightly larger than 12 cm DVDs) that split a single laser beam into signal and reference beams. A device called a spatial light modulator encodes data on the singular beam into a chessboard pattern of light and dark pixels. The hologram formed at the intersection of the reference and signal beams is recorded onto the optical disc. It is "etched" into the optical medium by a chemical reaction that occurs during the intersection. Changes in the reference beam angle, the wavelength, or the disc orientation produces different holograms. Tapestry Media discs can hold 300 GB worth of data, and even reaching up to 1.6 TB. InPhase Technologies [link], the creator of the technology, has managed to cram 515 gigabits into one square inch of media, compared to magnetic disks, a mere 37.5 gigabits.
Print Article
Send to a friend
Save as PDF