The Compact Disc

Because of the very favourable reception of the compact disc system, Philips felt it had a new world standard to replace the conventional (and vulnerable) gramophone record. Wisely, it came to a joint agreement with Sony to perfect the system. The first compact disc player went on sale in Japan in late 1982, and in Britain six months later. At that time, a player cost around £500 and the discs about £10. Now, just over four and a half years later, a reasonably good player can be bought for under £200, and it is expected that prices will be under £100 by Christmas. The discs have, however, risen slightly in price to about £12-14. Production technique The master (or blank) is made of a glass disc that is ground and polished to optical flatness- see Fig. 1. This is coated with a layer of photoresist, the thick- ness of which is controlled very accurately. The coating is oven- cured, after which the disc is ready for cutting. Strictly speak- ing, the term "cutting" is incor- re...