Patent ID: 6496468
Filing Date: 2002-12-17
Classification: B82Y,G11B

Abstract:
A near-field optical system, comprising:a medium holder adapted to hold an optical storage medium with a recording layer at a specified position; and an optical module to couple radiation to and from said medium holder and configured to include an objective lens and a near-field coupling element to guide an optical beam of a selected wavelength to said medium holder, said near-field coupling element disposed relative to said medium holder to effect evanescent optical coupling between said optical module and the optical medium placed in said medium holder, wherein said objective lens and said near-field coupling element are designed and positioned relative to each other to correct effects caused by refraction, lens aberrations, evanescent optical coupling, and a structure of the optical medium to focus said optical beam to a focusing plane spaced from said near-field coupling element by a predetermined distance greater than a distance between a location of the recording layer and the near-field element in absence of said optical medium and to focus said optical beam to or near the recording layer, wherein said optical module comprises a relay lens and an imaging lens for coupling said optical beam to said objective lens and said near-field coupling element, said relay lens and imaging lens spaced from each other by a distance smaller than a sum of focal lengths thereof to at least in part cause said beam to focus at said predetermined distance.