A LaserDisc player is a device designed to play video (analog) and audio (analog or digital) stored on LaserDisc. LaserDisc was the first optical disc format marketed to consumers. It was introduced by MCA DiscoVision in 1978. From 1978 until 1984, all LaserDisc player models read discs by using a helium–neon laser. In 1984, Pioneer Corporation introduced the first consumer player with a solid-state laser diode. This model, the Pioneer LD-700, was also the first LaserDisc player with a front-loading disc bay instead of a top-loading one. Pioneer became the market leader in LaserDisc technology. In the 1990s, Pioneer and others produced a small number of a high-definition video player models, which employed multiple sub-Nyquist sampling encoding (MUSE) technology. In 1996, Pioneer distributed their first DVD player in Japan, a combination Laserdisc/DVD player, model DVL-9. Pioneer announced the end of LaserDisc player production in January 2009. The last models Pioneer produced were the DVL-919 (an LD/DVD player), CLD-R5 (an LD/CD player), DVK-900 (an LD/DVD karaoke system), and DVL-K88 (an LD/DVD karaoke player).
Laser technology
Tube lasers The earliest players employed gas helium–neon laser tubes to read discs and had a red-orange light with a wavelength of 628 nm, while later solid-state players used infrared semiconductor laser diodes with a wavelength of 780 nm. Both the Magnavox Magnavision and the Pioneer LD players used the same model of laser tube. From 1978 to 1984, all LaserDisc players, either industrial or consumer, used helium-neon laser tubes.
Solid-state lasers In March 1984, Pioneer introduced the first consumer player with a solid-state laser, the LD-700. It was also the first LD player to load from the front and not the top. One year earlier Hitachi introduced an expensive industrial player with a laser diode, but the player, which had poor picture quality due to an inadequate drop-out compensator, was made only in limited quantities. After Pioneer released the LD-700, gas lasers were no longer used in consumer players, despite their advantages, although Philips continued to use gas lasers in their industrial units until 1985. Helium-Neon gas lasers had a shorter-wavelength laser that created a much smaller spot on the disc, leading to better tracking of imperfectly manufactured discs, such as an off-center hole punch or slightly eccentric tracks. The use of a solid state laser diode necessitated the introduction of the tilt-servo mechanism in LD players; this physically tilted the entire laser table, keeping it parallel with the disc, thus ensuring the larger laser beam spot was always perfectly circular and helping to reduce or eliminate crosstalk on warped CLV discs. In addition, the gas laser was less sensitive to external vibration, a must in certain industrial environments, and generated less photon-shot noise than the solid-state laser diode, resulting in a cleaner, less "busy" on-screen image.
Picture quality The picture produced by the LD-700's laser could be instantly recognized at the time; it was slightly softer, and large expanses of color in the image, such as a blue sky, would show streaking artifacts. Also, the infrared laser did not cope as well with disc manufacturing defects, such as dirt trapped under the surface of the disc (inclusions), an off-center hole or track errors created during mastering, such as track-to-track "kissing" (tracks touching). Because of this, collectors with large MCA DiscoVision collections (DiscoVision discs had just those type of above mentioned defects) tended to use tube-based LaserDisc players, since they played these discs better. In addition to being the first LaserDisc player to use a laser diode, the Pioneer LD-700 was also the first player ever to have the aforementioned "tilt" servo, which was arguably one of the greatest advances in LaserDisc players, providing superior tracking.
Mechanisms for changing discs Most LaserDisc players required the user to manually turn the disc over to play the other side. A number of players (all diode laser based) were made that were capable of playing both sides of the disc automatically; at the end of the first side, or at the viewer's command, the machine would reverse the direction of the disc's rotation, simultaneously moving the laser pickup head to the other side of the disc, and then initiate playback. Since LDs are made up of two single sided discs glued together, the auto-reverse player would center each disc side individually. LaserDisc players used either a simple U-shaped reversing mechanism, known as "Epsilon Turn", or technique known as "Gamma Turn", where the player physically rotated the laser reading head 180° as it moved from one side of the disc to the other, ensuring that the laser retained the same playback orientation on both sides of the disc. Some players even had twin laser reading circuits to eliminate excessive servos.
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