<P> The CD - ROM format was developed by Sony and Denon, introduced in 1984, as an extension of Compact Disc Digital Audio and adapted to hold any form of digital data . The CD - ROM format has a storage capacity of 650 MB . Also in 1984, Sony introduced a LaserDisc data storage format, with a larger data capacity of 3.28 GB . The DVD format, developed by Panasonic, Sony, and Toshiba, was released in 1995, and was capable of holding 4.7 GB per layer . </P> <P> The first Blu - Ray prototype was unveiled by Sony in October 2000, and the first commercial recording device was released to market on April 10, 2003 . In January 2005, TDK announced that they had developed an ultra-hard yet very thin polymer coating ("Durabis") for Blu - ray discs; this was a significant technical advance because better protection was desired for the consumer market to protect bare discs against scratching and damage compared to DVD . Technically Blu - ray Disc also required a thinner layer for the narrower beam and shorter wavelength' blue' laser . The first BD - ROM players (Samsung BD - P1000) were shipped in mid-June 2006 . The first Blu - ray Disc titles were released by Sony and MGM on June 20, 2006 . The first mass - market Blu - ray Disc rewritable drive for the PC was the BWU - 100A, released by Sony on July 18, 2006 . </P> <P> The most important part of an optical disc drive is an optical path, placed in a pickup head (PUH), usually consisting of a semiconductor laser, a lens for focusing the laser beam, and photodiodes for detecting the light reflected from the disc's surface . </P> <P> Initially, CD - type lasers with a wavelength of 780 nm (within the infrared) were used . For DVDs, the wavelength was reduced to 650 nm (red color), and for Blu - ray Disc this was reduced even further to 405 nm (violet color). </P>

What type of laser is used in cd and dvd players