Blu-ray (or BD for short) is an optical disc format used for storing data and high-definition video. Data from BD can be read, recorded or re-written depending on the disc type (BD-ROM, BD-R, BD-RE). Each Blu-ray disc can hold approximately ten times the storage of a DVD at 50GB. A 50GB Blu-ray disc can hold roughly 20 hours of audio and video.
Blu-ray operates with high definition audio and 1080p high definition video. These high-density discs first appeared on the market in 2006 and were developed by industry leaders that make up the Blu-ray Disc Association headed by Sony.
Blu-ray was involved in a high definition optical disc format war with HD DVD (High Definition Digital Versatile Disc). The HD DVD jumpstarted the high definition market as Blu-ray was initially more expensive and problematic. However, the tide significantly shifted in this format war when Sony decided to include a BD player in their wildly popular Playstation3 console.
Alliances between major players in the technology and entertainment industries moved format favor toward Blu-ray as well. Retailers quickly followed suit, and HD DVD developers conceded to Blu-ray in 2008.
As the next generation succeeding CDs and DVDs, Blu-ray uses similar concepts in its engineering. BDs employ close to the same physical dimensions as a DVD. DVDs consist of two 0.6mm discs flanking a recordable data layer, while Blu-ray uses just one 1.2mm polycarbonate disc, which therefore reduces the manufacturing costs.
The disc stores digitally encoded video and audio data in spiraled grooves on the polycarbonate layer. A drive's laser follows these grooves to read microscopic indentations (called pits) which interpret the disc's encoded information as the user's movie, music, game, computer data or other multimedia presentation. Compared to a DVD, the grooves are thinner and come packed at a higher density. Blu-ray has a data transfer rate of 36 Mbps compared to a DVD's 10 Mbps.
To fit more data within the same dimensions, the data layer is closer to the outer surface and laser. The layers of a DVD can be prone to laser beam distortion, whereas the Blu-ray recording layer's proximity to the surface removes these readability issues. Each BD is coated with a tough, clear polymer that contributes to its scratch-resistant and durable shelf life.
Blu-ray draws its name from the blue laser that's required to read the disc's information. Blue lasers have a shorter wavelength at 405 nanometers than the DVD's red laser at 650 nanometers. A smaller beam focuses on the pits in the grooves with higher accuracy and precision. The blue laser is also twice as thin as the DVD's red laser. Blu-ray eliminated the "e" from its name for trademark purposes.
Blu-ray discs will only operate on a Blu-ray player, Blu-ray drive or a Sony PlayStation 3 game console. A BD drive has varying measures of backward compatibility for CDs and DVDs because certain specifications are not required and are up to each manufacturer. However, since DVD is still a popular medium, most BD devices are backward compatible with the disc format.
Please use the links below to learn more about the different Blu-ray formats:
- BD-ROM - A Read-Only format that is used primarily for home video.
- BD-R - The single-use recordable Blu-ray explained in detail.
- BD-RE - Information about re-enscriptable Blu-ray discs and how they work.
- BD-XL - The most up-to-date information on extra large capacity Blu-ray discs.
- Printable BDs - Overview of the different types of printable Blu-ray discs.
- Blu-ray 3D - The latest information on three-dimensional Blu-ray movies.