Blu-Ray is a new type of DVD, developed in 2006. It can store many times more information than a standard DVD.
A typical DVD contains about 4.7 gigabytes of information. High-definition (HD) movies have much clearer resolution—and they require about five times as much space.
Blu-Ray can store enough information to play an HD movie and features. You can also download subtitles and other features on the Web; edit, reorder, and make playlists from recorded programs; record one program while watching another; and skip instantly anywhere on the disc.
The information on a DVD is stored as a series of pits or bumps on the recording surface. On top, the information appears as pits; on the bottom, you see protruding bumps. To play the movie, a laser reads the bumpy side.
The more bumps packed onto a disc, the more information can be stored. The bumps on a Blu-Ray disc are much smaller than on a standard DVD, so more information fits on one space.
Instead of a red laser, Blu-Ray players use a blue laser. Blue light has a shorter wavelength than red light, making the laser more sensitive. It’s capable of reading much smaller indentations than a red laser.
On a standard disc, the information is stored between two polycarbonate layers. This can cause problems, however. Occasionally, the polycarbonate can split the laser beam, making the disc impossible to read. Readability also suffers if the disc isn’t exactly perpendicular to the beam: a problem called “disc tilt.”
To combat this, Blu-Ray discs store their information on top of a polycarbonate layer. This prevents the beam from splitting and puts the information closer to the source of the laser, so disc tilt isn’t an issue.
Blu-Ray discs have more storage space and features than typical DVD’s. But their manufacturing costs are not significantly more, so a Blu-Ray disc is not significantly more expensive than a standard DVD. With all these benefits, it’s possible Blu-Ray will play a major role in the future of DVD’s.