Using a Blue Optical Laser
The key difference between a Blu-Ray player and a DVD player is that the Blu-Ray uses a blue optical laser instead of the red laser used by a DVD player. The blue laser has a smaller wavelength than the red laser (405 nanometers, compared to the red laser's 650 nanometers), allowing it to be focused more precisely so that it can read data stored in smaller packets. The smaller wavelength combined with the smaller data packet size allows for not only a greater amount of data to be stored but also for faster reading of the data as the disc spins.
Construction of Blu-Ray Discs
Because of the differences between a Blu-Ray player's blue laser and the red laser used by DVD players, Blu-Ray discs are constructed differently than DVDs. Whereas a DVD has its data layer contained between two layers of polycarbonate plastic, a Blu-Ray disc has its data layer on top of a single layer of polycarbonate. A hard protective layer is then placed over the data layer to protect it from scratches and fingerprints. Placing the data layer on top of a single polycarbonate layer instead of between two layers allows the disc to be read more easily by the Blu-Ray player while preventing errors that can occur due to refraction or an uneven application of the disc layers.
Reading Blu-Ray Discs
When a Blu-Ray disc is inserted into a player, the player's laser will scan the data packets near the center of the disc to get all of the basic information that it needs to play the disc. This data also contains information about how the disc is encrypted, allowing the player to decrypt the data, which was originally encrypted as a measure against piracy. Once the player has the necessary data and encryption details it can then begin playing the disc, reading the data packets as the disc spins and converting them to digital video and audio information. This information is then sent to the television, monitor or other device connected to the Blu-Ray player, generally through the use of separate component cables or an HD cable connection.