Evolution
| Mr. Hiren H. Patel 09MCA26, FYMCA |
VHS: analog
DVD: digitalM
BD: high-definition
Enables recording, rewriting, and playback of high-definition video.
Capable of storing information that the DVD and CD are not capable of holding.
Foundation
Blu-ray disc (BD) is appropriately named after the blue laser used to write the data.
The first blue laser was developed in 1996 by Shuji Nakamura (Nichia Corporation).
In 2002, an alliance was formed, called the Blu-ray Disc Association, including the likes of Sony, Samsung, Sharp, Hewlett-Packard, and Royal Phillips.
The "e" is intentionally left out of the name due to trademark restrictions.
Disc Characteristics
Single layer: 25 GB
Dual layer: 50 GB
Diameter: 120 mm
Thickness: 1.2 mm
Center hole diameter: 15 mm
Uses GaN laser of wavelength 400 nm
The smaller laser, compared to the DVD and CD, keeps the process more efficient (~5 mW).
The power conservation allows the development of multi-layer platforms and high-speed recording.
BD-ROM: read-only format.
BD-R and BD-RE: recordable formats (RE: rewritable; R: recordable once).
Numerical Aperature measures the ability of a lens to gather and focus light. As the numerical aperture increases, the focusing power increases and the beam size decreases.
Phase change implies that the disc section is either an amorphous or crystalline state. The reflectivity changes accordingly thus representing a binary bit.
Compatibility
This issue has introduced a competitor, the HD-DVD, that based its technology around being compatible with the DVD.
Recently the BDA has developed recorders that are BD/DVD/CD compatible.
JVC has advanced the BD by developing a BD/DVD combo disc that stores both DVD and BD data. It is composed of two DVD layers and a third BD layer storing 33.5 GB total.
Protection System
HDTV contains a copyright bit that is detected by the BD recorder. If the broadcast has no copyright bit, then the BD recorder is allowed to store the information.
Uses the Data Encryption Standard (DES) that has a key length of 56 bits.
A Key Block and Disc ID are written into the ROM area to prevent illegal copying.
Enhancements
Error rates increased in reading and writing after the original BD suffered scratches and fingerprints.
For protection, the prototype BD was enclosed in a case.
The case increased the size of the disc drive.
A hard coat was derived of an ultraviolet-curable resin that has a scratch resistance similar to the DVD.
An artificial fingerprint reagent is placed on the disc surface to resist fingerprint oils.
