US Patent 7239587 Approximating topology of optical disc surface

A method of one embodiment of the invention is disclosed that outputs an oscillating wave towards a surface of an optical disc. A proximity signal is detected in response to the oscillating wave being output towards the output of the optical disc, and denotes closeness of the oscillating wave to the surface. A number of peaks within the proximity signal are determined. Each peak corresponds to the oscillating wave crossing the surface of the optical disc. The time at which each peak within the proximity signal occurs is correlated with a value of the oscillating wave at that time, yielding a number of time-value pairs. The topology of the surface of the optical disc is approximated from these time-value pairs.