Sensing and control in optical drives how to read data from a clear disc

Optical storage devices, such as the compact disc (CD) and digital versatile disc (DVD), are consumer products with control components. In optical storage, data is represented on a plastic disc by the existence or absence of pits, whose reflective characteristics are different from those of the surrounding disc media. Data is read from the disc by reflecting light off the disc to detect these differences. The maximum data transfer rate is directly related to how well the servo systems perform to keep the read/write elements centered over the desired data and at the correct focus.