compact disc reading

During playback of a compact disc, a sensor analyzes laser beam variations reflected by the disc’s surface to re-create the original sound signal.

aluminum layer

The surface of the disc is covered with a thin layer of aluminum, which reflects the laser beam toward the sensor.

laser beam

Highly concentrated light beam that scans the surface of a disc; the pits and asperities determine how the light beam is reflected.

resin surface

Transparent film that covers and protects the aluminum layer.

objective lens

Optical system made up of a set of lenses attached to a mount; it focuses the laser beam onto the section to be played.

asperity

Each of the small protuberances of varying length that encode data on the disc’s surface.