Blu-ray

1. INTRODUCTION
Blu-ray is a new optical disc standard based on the use of a blue laser rather than the red laser of today’s DVD players. The standard, developed collaboratively by Hitachi, LG, Matsushita (Panasonic), Pioneer, Philips, Samsung, Sharp, Sony, and Thomson, threatens to make current DVD players obsolete. It is not clear whether new Blu-ray players might include both kinds of lasers in order to be able to read current CD and DVD formats.
The new standard, developed jointly in order to avoid competing standards, is also being touted as the replacement for writable DVDs The blue laser has a 405 nanometer (nm) wavelength that can focus more tightly than the red lasers used for writable DVD and as a consequence, write much more data in the same 12 centimeter space Like the rewritable DVD formats, Blu-ray uses phase change technology to enable repeated writing to the disc.
Blu-ray’s storage capacity is enough to store a continuous backup copy of most people’s hard drives on a single disc. The first products will have a 27 gigabyte (GB) single-sided capacity, 50 GB on dual-layer discs. Data streams at 36 megabytes per second (Mbps), fast enough for high quality video recording Single-sided Blu-ray discs can store up to 13 hours of standard video data, compared to single-sided DVD’s 133 minutes. People are referring to Blu-ray as the next generation DVD, although according to Chris Buma, a spokesman from Philips (quoted in New Scientist) “Except for the size of the disc, everything is different.”
Blu-ray discs will not play on current CD and DVD players, because they lack the blue-violet laser required to read them. If the appropriate lasers are included, Blu-ray players will be able to play the other two formats. However, because it would be considerably more expensive, most manufacturers may not make their players backward compatible. Panasonic, Philips, and Sony have demonstrated prototypes of the new systems.
2. EVOLUTION OF OPTICAL REMOVABLE MEDIA STORAGE DEVICES
2.1 Optical Storage
Optical RMSD formats use a laser light source to read and/or write digital data to a disc. Compact disc (CD) and digital versatile disc (DVD, originally referred to as digital video disc) are the two major optical formats. CDs and DVDs have similar compositions consisting of a label, a protective layer, a reflective layer (aluminum, silver, or gold), a digital-data layer molded in polycarbonate, and a thick polycarbonate bottom layer.
CD Formats include
• Compact disc-read only memory (CD-ROM)
• Compact disc-recordable (CD-R)
• Compact disc-rewritable (CD-RW)
DVD formats include
• Digital versatile disc-read only memory (DVD-ROM)
• Digital versatile disc-recordable (DVD-R)
• DVD-RAM (rewritable)
• Digital versatile disc-rewritable (DVD-RW)