| In 1978, Philips and Sony joined forces to produce the
Red Book audio CD standard. Philips had developed commercial laser disc players and Sony
had been researching digital recording for the ten years previous to CD-standard creation.
Instead of clashing to form incompatible laser disc formats, they joined forces to create
consensus with a single audio technology. In 1982, they announced the standard disc - the
4.72-inch format which we currently use today. It has a 120mm diameter and is 1.2mm thick.
The size was chosen (legend has it) because it could contain Beethoven’s Ninth
Symphony. An audio CD is a single sided media that stores data by a series of optical marks or "pits"; one reflects a low-powered layer laser off of this side to restore the saved data. A light receptor detects whether a reflection is strong or absent, and passes the data along to the microprocessors that translate the light patterns back into data or sound. This data is etched in a spiral track 1.6 microns wide, which leads to a track density of 16,000 tracks per inch. The whole CD contains a single spiral track nearly three miles long! |