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The Philips development of the videodisc technology began in 1969 with efforts by Dutch physicists Klaas Compaan and Piet Kramer to record video images in holographic form on disc. [12] [13] Their prototype Laserdisc shown in 1972 used a laser beam in reflective mode to read a track of pits using an FM video signal. Together with MCA, Philips ...
Most first-generation disc devices had an infrared laser reading head. The minimum size of the laser spot is proportional to the wavelength of the laser, so wavelength is a limiting factor upon the amount of information that can be stored in a given physical area on the disc. The infrared range is beyond the long-wavelength end of the visible ...
The earliest players employed gas helium–neon laser tubes to read discs and had a red-orange light with a wavelength of 632.8 nm, while later solid-state players used infrared semiconductor laser diodes with a wavelength of 780 nm. In March 1984, Pioneer introduced the first consumer player with a solid-state laser, the LD-700.
The optical drives in the photos are shown right side up; the disc would sit on top of them. The laser and optical system scans the underside of the disc. With reference to the top photo, just to the right of image center is the disc motor, a metal cylinder, with a gray centering hub and black rubber drive ring on top.
UDO systems use a blue-violet laser operating at a wavelength of 405 nm, similar to the one used in Blu-ray Disc, to read and write data. Conventional MOs use red lasers at 660 nm. [7] The blue-violet laser's shorter wavelength makes it possible to store more information on a 13 cm sized UDO disc.
A red laser is used as the reference beam to read servoinformation from a regular CD-style aluminium layer near the bottom. Servoinformation is used to monitor the position of the read head over the disc, similar to the head, track, and sector information on a conventional hard disk drive. On a CD or DVD this servoinformation is interspersed ...
The polycarbonate disc contains a spiral groove, called the pregroove because it is molded in before data are written to the disc; it guides the laser beam upon writing and reading information. The pregroove is molded into the top side of the polycarbonate disc, where the pits and lands would be molded if it were a pressed, nonrecordable Red ...
The purpose of LightScribe is to allow users to create direct-to-disc labels (as opposed to stick-on labels), using their optical disc writer. Special discs and a compatible disc writer are required. Before or after burning data to the read-side of the disc, the user turns the disc over and inserts it with the label side down. The drive's laser ...