Blu-ray:The future of Optical Storage
In current generation every one want to store large amount of High Definition data as much as possible in a single optical device, so to full fill this purpose Blu-ray Disc is invented .Even though in market there are many optical device like CD, DVD, HD-DVD but Blu-ray Disc provide better utilize space compare to above devices and it has capacity to store data up to 25 GB in a single layer and 50 GB in a dual layer. The dual layer Blu-ray disc can contain over 9 hours of high-definition video or about 23 hours of standard-definition video on a 50GB disc.
Blu-ray discs (BD) obtain their name from a grouping of the words blue and optical ray. The format was developed by the Blu-ray Discs Association (BDA), which is made up of a group of leading consumer electronics, major film studios and PC Companies.
The Blu-ray disc which is mainly use in high definition storage, enabled by a blue laser that has a shorter wavelength than the standard red laser used in CD (780nm) and DVD (650nm) technology. Blu-ray disc utilizes a blue laser with a wavelength of only 405nm combined with a strong lens system with a numerical aperture of 0.85. This results in an ultra-small laser spot which allows writing smaller data pits which increases the amount of data on the disc. Due to the small data entry spot on the disc surface hard coating is needed on Blu-ray disc. The disc has the same physical dimensions as standard DVDs and CDs.