HD-DVD (High Definition Digital Versatile Disk) – blue laser optical disk

Despite High Definition Digital Versatile Disc HD-DVD) being the original DVD Forum approved successor to the DVD format, it was ultimately doomed, eventually consigned to history by the rival Blu-ray Disk (BD) technology. Originally called Advanced Optical Disc (AOD), the technology’s basic format specifications were developed and proposed jointly by Toshiba and NEC. These define an optical disc that uses state-of-the-art blue-violet laser technology to enable extremely large-capacity recordings and high speed data transfer rates. Although primarily designed as a high-definition consumer video recording format, its very high storage capacities and high-speed data transfer rates also make HD-DVD suitable for storage libraries and ultimately other applications. An HD-DVD disc has the same physical size as a DVD, but has higher data and track densities that give it between roughly three to six times the storage capacity of a standard 4.7GB DVD-R. This feat is made possible using a 405nm blue-violet laser, actually violet-purple, and an optical pickup head with a 0.65 numerical aperture (NA) lens. Because a blue-violet light laser has a shorter wavelength than the red light’s 650nm, used in CD and DVD systems, it allows the laser beam to make a smaller spot on the disc surface. With each bit of data taking up less space on the disc, more data can be stored on a 4.7in disc. (For comparison with the light wavelengths depicted above, a human hair averages around 100,000nm thick). The HD-DVD format offered significantly less capacity than the Blu-ray technology, using low-bit-rate encoding technology such as MPEG-4 to store 9GB of high-definition video content onto a dual-layer DVD. However, HD-DVD’s big advantage over...

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