Patent ID: 6034929
Filing Date: 2000-03-07
Classification: G11B

Abstract:
A method 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 method comprising the steps of:providing a source of laser light;controlling the position of said laser light source;splitting said light into a first beam for writing and a second beam for reading;focusing said first beam onto a specific layer within said medium;varying said focusing of said first beam in an oscillatory manner towards and away from said medium, at a first frequency, .omega..sub.R ;directing said second beam to reference track edges within said medium;varying the point of impingement of said second beam in a back and forth manner across said track edges in an oscillatory manner at a different, second frequency, .omega..sub.T ;directing into a first photodetector laser light from said first beam which has been reflected from said medium;extracting signals from said photodetector to provide control for positioning of said laser light source with respect to focusing within a layer of said medium;directing into a second photodetector laser light from said second beam which has been reflected from said medium; andextracting signals from second photodetector to provide control for positioning said laser light source with respect to said reference tracks.