Patent ID: 7190656
Filing Date: 2007-03-13
Classification: G11B

Abstract:
1. A holographic apparatus comprising: a transferring unit for receiving an incident laser beam including data read from a plurality of tracks on a holographic medium to produce a focused laser beam; a tracking servo unit for receiving a first portion of the focused laser beam through a plurality of pinholes and, at the same time, reflecting a second portion of the focused laser beam back to the transferring unit through a reflecting section, wherein the tracking servo unit moves the transferring unit or the pinholes to adjust the amount of the first portion of the focused laser beam to thereby retrieve data from a target track among the plurality of tracks, and wherein the second portion of the focused laser beam reflected back to the transferring unit is converted into a return laser beam by the transferring unit; and a focusing servo unit for focusing the return laser beam and then checking a focused image of the return laser beam to compensate for vertical movements of the holographic medium.