Digital Versatile Disc (DVD)
Digital Video Disc or Digital Versatile Disc (DVD) is also an optical storage device that looks the same as a compact disc but is able to hold about 15 times as much information and transfer it to the computer about 20 times as fast as a CDROM. The CD and DVD have the same dimensions.
DVDs come in two formats: the DVD-Video and the DVD-ROM (DVD Read Only Memory) format. The DVD-Video format is used for home movie entertainment through a DVD player.
Why DVD stores more data than CD? Please note that DVD uses 650 nm (red) wavelength laser diode light as opposed to 780 nm for CD (infra red). This permits a smaller pit to be etched on the media surface compared to CDs (0.74 µm for DVD versus 1.6 µm for CD), allowing in part for DVD’s increased storage capacity. Further, the Blu-ray Disc, the successor to the DVD format, uses a wavelength of 405 nm, and one dual-layer disc has a 50 GB storage capacity. So basically, it is the laser optics that matters in storage capacities of various kinds of Discs. |
