The History of Blu-ray and how they work?


The Blu-ray Disc or BD is the next generation of optical disc with a data storage capacity of 25 (single layer) or 50 Gbytes (for dual layer discs). The name Blu-ray name comes from the colour of the laser (actually more of a violet colour)  used for reading the disc data, the laser diode used is based on either indium gallium nitride or gallium (III) nitride, and have  a wave length of 360 – 480 nanometres.

The Blu-ray disc  was a collaborative development by the members of the Blu-ray Disc Association, and as with the VHS and Betacam video formats wars of the 1970’s there was also an alternative format developed by Toshiba, this being HD DVD (based around compressing high definition content on to a DVD-9 dual layer disc) and backed by the DVD Forum, but after the film studio Warner Brothers announced that they would be only releasing titles on Blu-ray (having previously supported both formats), Toshiba acknowledged defeat in early 2008, announcing that they would cease development of both HD DVD players and computer drives.

So how does Blu-ray work? A DVD disc uses a 650 nanometer red laser and a CD operates with 780 nm laser, while a  Blu-ray disc uses a shorter wave length blue laser of 405 nanometers. The reduced wavelength means that a Blu-ray disc can store 5 times as much data. After that the playing principles are the same, with the data stored as varying length pits, which the laser can interpret via the reflective layer behind.

As with CD and DVD before it, there a number of variants to Blu-ray, so far we have outlined the details of the manufactured Blu-ray disc such as a Hollywood movie. The other variants include:

Blu-ray Disc recordable – BD-R and BD-RE

Like a DVD-R the BD-R is a write once recordable disc with a 25Gbyte data capacity, a BD-RE can be erased and burned again, many times.  Maximum writing speeds are up to 12x, but typical speeds are 4x and 6x.

Mini Blu-ray Disc

The main application for the mini Blu-ray disc is a BD-R format for camcorders, the capacity is 7.5 Gbytes.

BD9 and BD5

The idea behind these two formats was for using the same Blu-ray format but on either a DVD 5 or 9 as cheaper pressed disc, but in general the format has not caught on, and indeed although incorporated in to the BD-ROM format specification, none of the current Blu-ray players actually support the format officially, so there is no guarantee of the formats play ability.

BD XL

This format supports a huge 100 or 128 GByte write once capacity, there is also a 100 Gbyte re-writable version. The BD XL was defined in the BD-R 3.0 Format Specification in 2010. This is a multi layered disc designed for large data applications.

IH-BD

The Intra-Hybrid BLu-ray format is a two layer disc, having both  a 25GByte write once layer and a 25 Gbyte read only layer.

All Blu-ray discs use the Universal Disc Format or UDF 2.50 format for both PC and consumer player products.





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