Patent ID: 6824056
Filing Date: 2004-11-30
Classification: G02B

Abstract:
An auto-focus method for focusing an optical arrangement of a sub-micron optical system, the optical system including a head, at least part of the optical arrangement being included in the head, the optical arrangement being configured for reading from or writing to a surface of a medium, the head performing a scanning motion relative to the surface, the method comprising:(a) illuminating at least part of a first viewing region of the surface by the optical arrangement; (b) performing a focus range measurement of a second viewing region of the surface, said step of configuring and said step of performing being performed substantially at the same time, wherein a centroid of said first viewing region is offset from a centroid of said second viewing region at least in a direction which is parallel to a direction of relative motion of the medium and the head; (c) providing relative movement between the medium and the head in order for the optical arrangement to illuminate at least part of said second viewing region; and (d) adjusting the focus of the optical arrangement based upon said focus range measurement.