Laserdisc - Players

Players

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. Many Pioneer Model-III (DiscoVision PR-7820), VP-1000, LD-1100, LD-660 and PR-8210s are still in good working order. Both the Magnavox Magnavision and the Pioneer LD players used the same model of laser tube. Optical hobbyists have been known to cannibalize the laser tube machines. From 1978 to 1984, basically all LaserDisc players, either industrial or consumer, used Helium-Neon laser tubes.

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.

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.

Most machines made were single-sided and required the viewer 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 LD's 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. While Pioneer produced some industrial "jukeboxes" that held more than 50 discs, one company offered, for a short time in 1984, a "LaserStack" unit that required the user to physically remove the player lid for installation and attached to the top of the Pioneer LD-600, LD-1100 or the Sylvania/Magnavox clones. LaserStack held up to 10 discs and could automatically load or remove them from the player or change sides in around 15 seconds. A version for the Magnavox Magnavision and Pioneer VP-1000 was announced, as was a model for the front-loading players, but the company went out of business before the units were available. Only one consumer player, the LD-W1 (it was also released industrially too), was made that could hold more than a single disc; the W1 held two discs and could automatically change discs and sides by rotating the entire mechanism, including both the laser and turntable. Electrically, the LD-W1 was identical to the Elite LD-S1. The LD-W1 remained in the Pioneer catalog for many years and received many improvements: While the first version of the W1 had only 2X oversampling and 16-bit D/A converters in the digital audio, the later units had 4X oversampling with 20-bit D/A converters. The video noise reduction was improved, too, sharpening the picture and reducing disc noise while eliminating the artifacts it caused. In addition, high-frequency response in the FM video demodulator and A/D-D/A converters was extended and flattened, increasing resolution and reducing visible digital artifacts. The W1's player software was refined too, making disc and side-changing faster, plus, during side or disc changes, it grabbed a still-frame closer to the actual end-of-program instead of just any frame from the side's last five minutes.