While Toshiba and NEC are to propose an alternative to the DVD Forum, Blue-ray Disc - HD-DVD specification, it is more easily compatible with the existing DVD.
In November 2002, Taiwan's ITRI's Opto-Electronics also issued a third set of Blue-ray Disc, which is a separately similar program with Blue-ray Disc and HD-DVD. Opto-Electronics actively seeks support from the industry from the mainland, with a view to alleviate cross-strait CD-ROM industry in the pressure on the issue of royalties.
The above-mentioned three Blue-ray discs are 120mm diameter discs. In addition, Plasmon presents a so called UDO (Ultra Density Optical) Blue-ray Disc. This is a 5.25 "double-sided record with a casing of the CD-ROM and a capacity of 30GB-120GB.
The emergence of Blue-ray disc of the human indicates the progress in the optical storage technology. 4.7G DVD-discs can store 133 minutes by the MPEG2-encoded video information. With the emergence of high-definition video, DVD volume is too small. For example, 1 hour of high-definition digital TV programs require the storage capacity of about 12GB, to save a full 2 hours' HDTV program, CD-ROMs need 24GB capacity. It is expected that a new higher-capacity CD-ROM to appear. In order to improve the capacity of CD-ROM in the DVD disc, based on the information to further reduce the size of pits and shorten the distance, improve recording density, while, reduce the spot size, technicians use a shorter wavelength laser light source to increase the value of lens aperture, ensuring the laser head in high-density optical disc can accurately read and write data. CD, VCD use an infrared laser of 780nm in wavelength and DVD employs a red laser of 635nm ~ 650nm in wavelength While the new disc uses a 405nm wavelength laser - a Blue-Violet Laser deserving the name Blue-ray Disc.
|data transfer rate||36Mbps|
|diameter of disc||12cm|
|thickness of disc||1.2mm (1.1mm+0.1mm)|
|recording format||phase change recording|
|data track method||groove recording|
|minimum land-pit length||0.160/0.149/0.138μm|
|video format||MPEG2 video|
|audio format||AC3, MPEG1, Layer2|
|video and audio format||MPEG2 signal stream|
Blue-ray Disc, referred as BD, its specifications are as shown above. BD disc features are: It consists of a thickness of 1.1mm of the recording layer and a thickness of only 0.1mm composite made of a transparent protective layer. The work of the shorter wavelength light source, in the recording layer surface can be comparable with the operating wavelength of fingerprints; dust will read and write CDs a serious impact on the quality. Starting from the DVD disc, it is used in the substrate as a protective layer. Protective layer can protect the recording layer from being scratched, but also easily wipe the surface. BD's NA is 1.42 times larger than the big DVD, resulting in the optical axis and the optical disc recording surface tilt angle allows to narrow the scope of 2.9 times and the angle of inclination about 1.6 times of the permissible range. Tilt angle is inversely proportional to the thickness of the permissible range and CD-ROM, in order to obtain a more lenient to allow the scope, only the protective layer is reduced by the thickness of 0.1mm.