Optical Media Types - Page 3

Blu-Ray and HD-DVD

Probably the biggest format war of all was the one to be the successor to the DVD. The competing formats were the HD-DVD developed by Toshiba and Blu-Ray developed by the Blu-Ray Disc Association. Both formats offered increased disc capacity on a standard CD sized disc, enough capacity to hold a High-Definition Movie. HD-DVD was released first and gained a small market advantage the first high definition films were released on HD-DVD but the cost of a player was high and sales were slow. Blue-Ray was then developed and had the same problem. With two standards competing the price of hardware remained high and sales remained slow. There was however 1 major turning point, the Playstation 3. A games console that was released with a built in Blue-Ray player. With Millions of PS3's already guaranteed to be sold and now with the ability to play high-definition movies without a dedicated player, Blu-Ray slowly become victorious and the sole remaining supported High-Def format.

Now Blu-Ray has progressed like all the previous disc formats into a recordable optical medium for the home user. Now a single disc can be used to store up to 25GB single layer and 50GB dual layer.

Blu-Ray Media

Abbreviation	Full Version	Notes
BD-ROM	Blu-Ray Disc - Read Only Memory	The first Blu-Ray spec disc was the ROM, following the previous disc formats this is the manufacturers ready pressed format for distributing data or films etc which are unable to be modified. Used for Blu-Ray films you buy in the shops and Playstation 3 games.
BD-R	Blu-Ray Disc - Recordable	Again much the same as CD and DVD, Blu-Ray has a WORM (Write Once Read Many) format the BD-R. A layer of organic dye is used on top of the disc in order for a home Blu-Ray writer can burn data into the disc. BD-R discs can be 25GB single Layer and 50GB dual layer.
BD-RE	Blu-Ray Disc - ReRecordable	BD-RE allows the home user to have a Blu-Ray disc with all of the capacity of the BD-ROM or BD-R but also have the ability to re-record to the disc around 1000 times making it a viable portable storage device with enough capacity to store a high definition movie. Its draw back of course will be it could only be used on computers with a Blu-Ray drive or Blu-Ray players that support BD-RE.
BD-R LTH	Blu-Ray Disc - Recordable Low to High	Brought in later than the other formats, BD-R LTH offered a cheaper solution to Blu-ray manufacturers. This format could be created on older machines designed to create DVD's. Slight modifications were required to current machines instead of requiring to buy brand new ones. Its only downfall was that older Blu-Ray drivers and players were either not compatible with this format or required at least a firmware upgrade.

Blu-Ray Technology

Blu-Ray technology is very similar to that of DVD technology, in the way that it uses a laser to read changes in the surface of a disc. These changes represent binary code which in turn translates into the information that you get out of the disc. DVD's use a red laser to read the optical discs, Blu-Ray gets its name from using a blue (or more accurately a violet) laser to read the discs. Blue lasers have a shorter wavelength of 405nm compared with that of a red laser using 650nm for DVD's.

Because of the shorter wavelengths of the lasers in Blu-Ray players and other factors such as less diffraction the Blu-Ray laser can be pin-pointed more accurately on a disc, allowing tracks to be formed closer together, ultimately allowing for more data to be stored on an optical disc. Going back to the diffraction for a second, to limit the effect of diffraction Blu-Ray discs have a very thin top coating to protect the disc. This can be a problem if not looked after correctly as scratching can be very damaging to a Blu-ray disc. So much so in fact that early Blu-Ray discs were placed in cartridges to protect them. Since then hard-coating has been introduced with a scratch resistant surface in order to protect the vulnerable surface. These required factors do pump of the price of a Blu-ray disc however and are one of the factors behind Blu-Ray being more expensive than DVD's.

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