What is Blu-Ray ?

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How Much Data and Video Can You Fit On A Blu-Ray Disc?


While current optical disc technologies such as DVD, DVD±R, DVD±RW, and DVD-RAM rely on a red laser to read and write data, the new format uses a blue-violet laser instead, hence the name Blu-ray. Despite the different type of lasers used, Blu-ray products can easily be made backwards compatible with CDs and DVDs through the use of a BD/DVD/CD compatible optical pickup unit. 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 even 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 even though it's the same size as a CD/DVD. This together with the change of numerical aperture to 0.85 is what enables Blu-ray Discs to hold 25GB/50GB.

- About 9 hours of high-definition (HD) video can be stored on a 50GB disc.
- About 23 hours of standard-definition (SD) video can be stored on a 50GB disc.


Physical size	Single layer capacity	Dual layer capacity	layer capacity (Sextuple)
12 cm, single sided	25GB (23.3GiB)	50GB (46.6GiB)	200GB (33.3GB/layer) TDK
12 cm, double sided	50GB (46.6GiB)	100GB (93.2GiB)
8 cm, single sided	7.8GB (7.3GiB)	15.6GB (14.5GiB)
8 cm, double sided	15.6GB (14.5GiB)	31.2GB (29GiB)

A single sided Blu-ray disc has the storage capacity of 25GB. A dual layer Blu-ray disc has the storage capacity of 50GB. Blu-ray technology has the possibility of reaching 200GB on a single disc.

TDK recently announced that they have created a working experimental Blu-ray Disc capable of holding 200 GB of data on a single side (six 33 GB data layers).

[source: Wikipedia; http://en.wikipedia.org/wiki/Blu_ray]



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