3M into Videodiscs
by David Lachenbruch
Videodisc fever is spreading. One of America's top industrial firms, 3M, has decided to go into the mastering and pressing business "for any viable videodisc system." It will start before the end of 1980, its first project being the manufacture of industrial-educational discs for the Thomson-CSF optical system. Although this system has been out of the limelight for a year or more, it is one of the first to be developed. It differs from the technique used in the DiscoVision records played on Magnavox and MCA optical players in that its discs are trans missive rather than reflective. In the Magnavox-MCA players, the laser beam is reflected by the disc to a light-sensitive detector. Thompson's discs are transparent and the laser light shines through the disc to a detector on the other side, being modulated (like the reflective system) by pits in the disc. The French company claims three advantages to its system: (1) Being uncoated, the discs are simpler to manufacture, (2) The discs can be made thin and flexible and can be sent through the main in thin envelopes, (3) Both sides of a disc can be played in sequence without turning the record over - by simply refocusing the laser to play the far side after the near side is finished.