Patent ID: 6108282
Filing Date: 2000-08-22
Classification: G11B

Abstract:
An apparatus for controlling positioning of a laser light source for use with a recording medium which is susceptible of being modified by impinging laser light, said apparatus comprising:a source of laser light;means for controlling the position of said laser light source;a first beam splitter for dividing laser light from said source into a first beam for writing and a second beam for tracking;a lens for focusing said first beam onto a specific layer within said medium;means for varying said focusing in an oscillatory manner towards and away from said medium at a first frequency .omega..sub.R ;reflective means for directing said second beam to reference track edges within said medium;means for varying the point of impingement of said second beam back and forth across said tracks in an oscillatory manner at a different second frequency .omega..sub.T ;a second beam splitter for dividing said first beam into a writing beam for impinging on said medium and for directing, into a first photodetector, laser light from said first beam which has been reflected from said medium;a second photodetector for receiving laser light from said second beam which has been reflected from said medium;filter means for extracting signals from said first photodetector having spectra in the vicinity of .omega..sub.R to provide control for the positioning of said laser light source with respect to its focus position;and filter means for extracting signals from said second photodetector having spectra in the vicinity of .omega..sub.T to provide control for the positioning of said laser light source with respect to said tracks within said medium.