Patent ID: 7158274
Filing Date: 2007-01-02
Classification: G11B

Abstract:
1. A pick-up apparatus for a digital storage medium including a holographic storage medium in which a holographic property is used to reconstruct a holographic signal stored therein and a digital versatile disk in which a reflective property is used to read a reflective signal stored therein comprising: means for generating a first and a second beam each of which has different wavelength; means for propagating a reflected beam and a reconstructed signal beam through a propagation path, wherein the digital storage medium reflects the first beam to generate the reflected beam having the reflective signal therein and a holographic interference pattern in the holographic storage medium diffracts the second beam to generate the reconstructed signal beam having the holographic signal therein; means for splitting the reflected beam from the propagation path to detect the reflective signal from the reflected beam; means for separating the reconstructed signal beam from the propagation path to detect the holographic signal from the reconstructed signal beam, wherein the propagation path is substantially perpendicular to the digital storage medium, wherein the propagating means includes an objective lens, faced with the digital storage medium, for converging the first beam on a reflective layer in the digital storage medium so that the reflected beam of the first beam is generated and receiving the reflected beam and the reconstructed signal beam to be propagated through the propagation path, wherein the propagating means further includes means for converting polarizations of the first beam, the reflected beam and the reconstructed signal beam from an S linear polarization to an S circular polarization, from an S circular polarization to a P linear polarization, from a P linear polarization to a P circular polarization or from a P circular polarization to an S linear polarization, and wherein the first and the second beam are introduced to the digital storage medium with a P and an S circular polarization, respectively, or the first and the second beam are introduced to the digital storage medium with an S and a P circular polarization, respectively.