An optical disc format jointly developed by the Blu-ray Disc Association (BDA), a group of consumer electronics, personal computer, and media manufacturers (including Apple, Dell, Hitachi, HP, JVC, LG, Mitsubishi, Panasonic, Pioneer, Philips, Samsung, Sharp, Sony, TDK and Thomson). The Blu-ray format was developed to enable recording, rewriting and playback of high-definition video as well as store large amounts of data. A single-layer Blu-ray disc can hold 25GB, which can be used to record over 2 hours of HDTV or more than 13 hours of standard-definition TV. There are also dual-layer versions of the discs that can hold 50GB.
Optical disc technologies such as DVD, DVD+/-R, DVD+/-RW, and DVD-RAM use a red laser to read and write data. The Blu-ray format uses a blue-violet laser instead. Despite the different type of lasers used, Blu-ray hardware is designed be made backwards compatible through the use of a BD/DVD/CD-compatible optical pickup that allows playback of standard CDs and DVDs. The benefit of using a blue-violet laser (405nm) is that it has a shorter wavelength than a red laser (650nm), which makes it possible to focus the laser spot with greater precision. This allows data to be packed more tightly and stored in less space, so it’s possible to fit more data on the disc.
Blu-ray was designed with HDTV in mind and supports direct recording of the MPEG-2 TS (Transport Stream) used by digital broadcasts, which makes it compatible with global standards for digital TV. This means that HDTV broadcasts can be recorded directly to the disc without any quality loss or extra processing. To handle the increased amount of data required for HD, Blu-ray employs a 36Mbps data transfer rate.
Blu-ray’s backers expect it to replace VCRs and DVD recorders with the transition to HDTV over the coming years. The format also has potential to become a standard for PC data storage and HD movies in the future.