What is Blu-Ray Disc ?
Blu-Ray, also known as Blu-Ray Disc (BD) is the name of a next-generation optical disc format. The format was developed to enable recording, rewriting and playback of High-definition video (HD), as well as storing large amount of data.
The Format offers more than 5 times the storage capacity of traditional DVDs and can hold upto 25GB on a single-layer disc and 50GB of a Dual-layer disc.
- Blu-Ray Disc (BD) is appropriately named after the blue laser used to write the data.
- The first blue laser was developed in 1996 by Shuji Nakamura (Nichia Corporation).
- In 2002, an alliance was formed called the Blu-ray Disc Association including the likes of Sony, Samsung, Sharp, Hewlett-Packard and Royal Phillips.
- It has One later, Two layer, Three layer, Four layer, Five layer, Six layer.
Variations and Sizes
- A single-layer Blu-Ray Disc (BD) has enough storage capacity (25GB) for approximately two hours of High-definition video with audio.
- A Dual-layer (50GB) BD can hold enough data for approximately four hours of HD video.
- TDK Corporation recently announced that they have created a working blu-ray capable of holding 200GB of data (Six 33GB single layers Discs).
Laser and Optics
- Blu-Ray Systems use a blue-violet laser operating at a wavelength of 405 nm, similarly to the one used for HD DVD, to read and write data. Conventional DVDs and CDs use Red and Infrared lasers at 650 nm and 780 nm respectively.
- Blu-ray has two types BD-R and BD-RE with the price $19.99 and $24.99 and $47.99 and $59.99 for 50GB respectively.
How Blu-ray Disc Works?
- Discs store digitally encoded video and audio information in pits— spiral grooves that run from the center of the disc to its edges. A Laser reads the other side of these pits — the bumps — to play the movie or program that is stored on the DVD.
- The more data that is contained on a disc, the smaller and more closely packed the pits must be. The smaller the pits (and therefore the bumps), the more precise the reading laser must be.
- Blu-ray uses a blue laser. A blue laser has a shorter wavelength (405 nanometers) than a red laser (650 nanometers). The smaller beam focuses more precisely, enabling it to read information recorded in pits that are only 15 microns (µm) (1 micron = 10-6 meters) long — this is more than twice as small as the pits on a DVD.
- Blu-ray has reduced the track pitchfrom 0.74 microns to 32 microns. The smaller pits, smaller beam and shorter track pitch together enable a single-layer Blu-ray disc to hold more than 25 GB of information — about five times the amount of information that can be stored on a DVD.
True High Density Density Recording
- Single layer: 25GB
- Dual layer: 50GB
- Diameter: 120 mm
- Thickness: 1.2 mm
- Center hole Diameter: 15 mm
- Uses GaN laser of wavelength 400 nm
- The smaller laser, compared to the
DVD and CD, keeps the process more
Efficient (~5 mW)
Hard Coating Technology
In January 2004 was introduced a clear polymer coating that gives Blu-ray Discs unprecedented scratch resistance. The coating was developed by TDK Corporation and is called as “Durabis”. It allows BDs to be cleaned safely with only a tissue.
To meet Blu-ray’s specifications, TDK’s coating had to be less than 0.1 mm thick, be hard enough to resist considerable damage, and yet be transparent enough to be easily read through. According to a filing with the U.S. Patent and Trademark Office, the process essentially spin-coats two layers onto discs. One is for protection against scratches, and the other protects against stains and oils.
While Blu-ray mandates the use of a scratch-resistant coating, it does not specify what coating is used, and both Sony and Panasonic have their own independent hard coating technologies that are primarily in use on Blu-ray pre-recorded discs.
A TDK spokesman says the present protective layer represents “the first generation” of the coating and that the company has been refining the technology to better suit Blu-ray Discs. Although it might seem possible to adapt the polymer to other uses in LCD, CRT, and plasma screens, TDK plans to target the DVD market for now, because scratches are so common on DVDs that in the rental market, they may only last about 12 to 13 rentals on average.
- This issue has introduced a competitor, the HD-DVD, that based its technology around being compatible with the DVD.
- Recently the BDA has developed recorders that are BD/DVD/CD compatible.
- JVC has advanced the BD by developing a BD/DVD combo disc that stores both DVD and BD data. IT is composed of two DVD layers and third BD layer storing 33.5 GB total.
- Record High-definition Television (HDTV) without any quality loss.
- Instantly skip to any spot on the disc.
- Record one program while watching another on the disc.
- Edit or Reorder programs recorded on the disc.
- Automatically search for an empty space on the disc.
- 3rd Generation disc which has High storage capacity.
- More Life-span due to the protecting layer.
- Very soon BD replaces CD’s & DVD’s.