Blu-Ray technology is the next generation of optical disc format developed by the Blu-Ray Disc Association(BDA) and major developers of consumer electronics, computers, and media manufacturers around the globe. The technology will enable consumers to store large amount of data (5 to 6 times more than DVD), record/rewrite digital content, and watch high definition videos via Blu-Ray devices. The Blu-Ray disc comes in two types: Single layer disc which will be introduced first in the market and dual layer disc which will follow near future. The single layer can hold up to 25 GB of data which equates to about 2 hours of recording/playing time of digital content on HDTV and 13 hours of non-digital content from a regular television. The dual layer disc will hold data up to 50 GB and it will be mainly utilized for gaming (PS3) and entertainment purpose.
The current optical disc technology such as DVD utilizes red laser to read and write data. However, the Blu-Ray technology uses blue- violet laser to read and write. There are several differences between the red laser and blue laser. First, the wavelength of a blue-violet laser is shorter (405nm) than the red laser (650nm). Second, the numerical aperture has been improved to 0.85 from .60. The shorter wavelength of a blue-violet laser leads to more accurate focus on the laser spot, which makes it possible to pack more data onto a DVD sized disc. The numerical aperture measures the ability of a lens to gather and focus light. The aperture number 1 represents the greatest focusing power and smallest laser spot. The DVD?s numerical aperture ranges from .50 to .65 compared to the Blu-Ray?s numerical aperture of .85, making it a big improvement over the existing optical disc technology.
The technology industry has seen an explosive demand for the HDTV and consumer’s desire to record high definition content. Fueling the demand is the U.S government’s mandate to shut off analog broadcast by February 17th of 2009 and replace it with digital broadcast. The Blu-Ray technology was created out of necessity to meet the new demand and to set a new standard in the field of optical disc. This technology supports direct recording of the MPEG-2 TS (Transport Stream) which is used by many digital broadcasters globally. In other words, digital content from HDTV can be recorded directly to the disc without compromising quality and extraneous processing power. Also, Blu-ray will support MPEG-4 in H.264, and SMPTE, Microsoft’s Windows Media Video. The Blu-Ray’s 1x speed is rated at 36Mbps which is less than the required 54Mbps for movies and games. Movies and game discs will utilize at least 2x speed, which is 72Mbps data transfer rate, to complement the large amount of data required for high definition content. This fast rate is more than sufficient to record and playback HDTV while maintaining the original picture quality. It is very possible to watch playback video and record HD video at the same time through the use of random access feature offered by the Blu-ray technology.