Compact Discs: How CDs work, how it was developed, the scientific principles involved (in terms of waves), and how they impact society.

Essay by sodamayHigh School, 11th grade November 2008

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Compact discs (CDs) were first introduced in the early 1980s as a medium to store and play music in a digital format. Before the invention of CDs, music and videos were stored as analog waves in cassette tapes, VCRs and gramophone records which were not as effective as CDs, storage and quality-wise. Now, we use CDs to store many other forms of data such as videos, photos, software, text documents and many other things. Some companies even produce CDs that come in unique and funky shapes, usually as a marketing novelty. CDs are light, cheap to manufacture and relatively reliable, making it an ideal form of storage.

A CD is a thin, circular sheet of polycarbonate plastic with a hole in the centre, similar to a doughnut. The polycarbonate plastic is stamped with a high-powered laser to form minuscule pits in a continuous spiral track on its reflective surface.

This forms the bumps which will be read by the laser in a CD player. The polycarbonate plastic is then coated with aluminium (or another metal such as gold) which acts as the reflector. A transparent plastic layer is then added to protect the CD from external damages like scratches, nicks and dust. All these layers add up to only 1.2mm with a diameter of 12cm, which is pretty amazing, considering the huge amount of data a CD can store.

Sony and Philips Consumer Electronics joined forces in 1979 to design a new digital audio disc. The taskforce was led by prominent engineers Kees Schouhamer Immink and Toshitada Doi and continued the research started by Philips in 1977 on laser technology and optical discs. A compact disc standard, the Red Book, was created a year later after much discussion and research. Philips contributed the general manufacturing...