The entire data content of a thermally erasable optical memory medium is erased simultaneously by irradiating the entire signal-retaining layer of the medium with light in such a manner that the signal-retaining layer is preferentially heated over other layers in the medium, particularly other thermo-optically...http://www.google.es/patents/US4970711?utm_source=gb-gplus-sharePatente US4970711 - Bulk eraser for optical memory media
