Blu-ray discs can hold multiple hours of HD content, with plenty of room to spare for the bonus features you may have grown accustomed to with DVD. The developers of Blu-ray couldn't make the disc physically larger, so in order to significantly increase the information storage capacity, they increased the data density. The information pits got smaller, and the spacing of the pit rows got tighter (see illustration below). The discs also have a super-thin transparent protective coating, which places the data layer closer to the disc's surface and thus closer to the laser. In order to read these much smaller data pits, Blu-ray players use a blue-violet laser, which has a shorter wavelength and a smaller "beam spot" than the red laser used in DVD players. The players also spin the discs at higher speeds for even faster data transfer.
Storing high-definition video requires much higher data density than standard DVDs allow. Blu-ray discs have smaller data "pits" and more closely spaced pit rows compared to DVDs and HD DVDs. Blu-ray players require a blue laser to read these smaller pits. In Blu-ray players, the laser's higher "numerical aperture" (NA) allows the beam to be focused to create a tighter spot for reading smaller pits.
Blu-ray duplication is the reproduction of Blu-ray optical disc with its content. Blu-ray optical discs are used in storing a hi-definition digital content such as music, movies, videos, text documents and files and...
Blu-Ray discs fit more, and do more than traditional DVD. Blu-ray discs provide much greater data storage capacity and faster bit rates than standard DVD. Translation: much improved picture and sound quality...
