An Optical Disc<\/a> is a flat, circular data storage medium that is read and written using Laser<\/a> technology. These discs are typically made of a Polycarbonate<\/a> substrate with a reflective metallic layer. The development of this technology was a joint effort between Sony<\/a> and Philips<\/a>, leading to the commercial release of the Compact Disc<\/a> (CD) in 1982. This innovation fundamentally changed the Music Industry<\/a> and eventually the way Computer Software<\/a> was distributed.<\/p> Data on an Optical Medium<\/a> is represented by microscopic Pits and Lands<\/a> arranged in a spiral track starting from the center. During playback, a Laser Diode<\/a> focuses a beam on the track. The Photodiode<\/a> within the Optical Drive<\/a> detects the intensity of the reflected light, which changes when the laser passes over a pit. For more technical specifications, refer to the Britannica entry on Optical Storage<\/a> and official documentation on Wikipedia<\/a>.<\/p> The first widely successful format was the CD-ROM<\/a>, which offered approximately 700 MB of storage. This was followed by the DVD<\/a> (Digital Versatile Disc), which utilized a shorter wavelength red laser to increase capacity to 4.7 GB. The third generation, Blu-ray Disc<\/a>, uses a blue-violet laser (405 nm) to achieve even higher data density, supporting High-Definition Video<\/a> and storage up to 100 GB. Specialized variants like the M-DISC<\/a> are engineered for long-term Data Archiving<\/a> due to their resistance to environmental degradation.<\/p>Physical Mechanisms<\/h2>
Evolution and Formats<\/h2>