Patent ID: 8531748

Claim:
A reflection-type holographic storage system with a coaxial common aperture arrangement of an object beam and a reference beam, in which the object beam and the reference beam are illuminated into a holographic storage medium by the same lenses, the object beam and the reference beam having a first wavelength, wherein the reflection-type holographic storage system comprises: a first light source for generating the object beam and the reference beam; a second light source for generating a servo beam having a second wavelength different from the first wavelength; an information channel; a reference channel; a dedicated servo channel, wherein the information channel is a finite conjugate system and the reference channel and the dedicated servo channel are infinite conjugate systems; and a lens system with a Fourier plane that coincides with a hologram layer of the holographic storage medium; wherein the lens system is configured to: Fourier transform the object beam into the hologram layer of the holographic storage medium; focus the reference beam into the hologram layer of the holographic storage medium; and focus the servo beam onto a servo area of the hologram layer; and wherein the lens system comprises: a moving part comprising three lenses, which is configured to Fourier transform the object beam into the hologram layer of the holographic storage medium and to focus the reference beam and the servo beam into the hologram layer of the holographic storage medium; and a fixed part, which is configured to pre-focus only the servo beam.