The DVD came out and revolutionized the movie industry in 1997; however, Blu-ray disc took the DVD experience to a whole new level. Because of the revolution of high definition video and audio televisions a new high-definition disc was needed.
A single-sided standard DVD holds about 4.7 gigabytes (GB) of information. Usually that is the size of an average two-hour, standard definition movies with added a limited space for extra features. However, new high-definition televisions takes up about five times more bandwidth and requires discs that have about five times more storage. So in came the new generation of disc, which is called Blue-ray.
A single Blu-ray disc can hold up to 27 GB of information, that's more than two hours of high-definition video and about 13 hours of standard definition video. Meanwhile, a double-layer Blu-ray disc can hold up to 50 GB of data, which can hold about 4.5 hours of high definition video and more than 20 hours of standard video.
Not only do Blu-ray discs have more storage capacity but they also bring a whole new level of interactivity. Users are able to connect to the Internet and download different features through the disc. You also can record high-definition television without any quality of loss, instantly skip any spot on the program and record one program while watching another on the disc. Other features include recording playlists, editing programs, and searching for empty space on the disc to avoid recording over a program.
The disc stores video and audio information in pits on the disc. The laser reads the other side of these pits to play the movie or program that is stored. The more data that is stored the more closely packed the pits are. The smaller these bumps are the more precise the reading laser needs to be.
Current DVDs use a red laser to read data. Blu-ray, of course, uses a blue laser. The blue laser has a shorter wavelength than the red. The smaller beam focuses more precisely and will be able to read information recorded in pits that are only 0.15 microns long - which is more than twice as small as the pits in a DVD.
DVD discs and Blu-Ray discs look alike and have the same thickness but the two store information very differently. DVDs store the data that is sandwiched between to polycarbonate layers. This causes birefringence in which the laser is separated into two separate beams. If the beam is split too much, the disc will not be read properly.
Blu-ray avoids this problem by placing data on top of a 1.1 mm-thick polycarbonate layer. With the layer being on top the birefringence is eliminated and allows better readability. There is a hard coating that is placed on the outside of the disc to prevent scratches and finger prints that can cause poor reading.
Overall, Blu-ray has a higher data transfer rate and can record a lot more data. This is what makes the new format so much better than its predecessor: the DVD.
