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| Polarization independent wavelength tunable filter based on birefringence compensation |
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| Wavelength division multiplexer and demultiplexer |
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| Tunable filtering device for optical communications |
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| Wavelength selection switches for optical application |
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| All-optical holographic code division multiple access switch |
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Method and apparatus for storage and retrieval with multilayer optical disks
| Details |
Inventors: Hasman, Erez; Friesem, Asher A.;
Assignee: Yeda Research & Development Co. Ltd. (Rehovot, IL)
Primary Examiner: Ben; Loha
Assistant Examiner:
Attorney, Agent or Firm: Friedman; Mark M.
A multilayer optical disk system, which includes an optical disk unit having a number of connected optical disks. A number of light sources, such as diode lasers, are used to provide a number of light beams of different wavelengths. A wavelength multiplexer combines the light beams into a single beam which is then axially dispersed so that light of different wavelengths are simultaneously focuses onto the different optical disks. A wavelength demultiplexer splits light reflected from the optical disks according to wavelength to produce separate beams which are then separately detected. |
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DETAILED DESCRIPTION The present invention offers a three-dimensional optical disk storage with significantly decreased crosstalk (high signal to noise ratio), and greatly reduced access time (increased bit-rate readout).
The present invention is characterized in that two or more, and preferably all, of the disks are read simultaneously using a parallel readout.
This approach offers a significant access time advantage over the movable lens approach described above, regardless of whether partially transparent disks or selective wavelength disks are used.
The present invention is of a novel three dimensional optical storage device which includes a multilayer optical disk.
In one embodiment, the media of each layer are wavelength dependent, such that each layer may have high transmission for one wavelength or band of wavelengths and high reflectivity for a different wavelength or band.
The optical head of a system according to the present invention includes an incident light system which combines two or more light sources, which may be diode lasers, each light source emitting a beam of light of a different wavelength which is related to the selective wavelength media of the multilayer optical disk, for readout of the desired disk information.
The combining of several beams into a single beam, is effected using a suitable wavelength multiplexing device which may include dichroic beam combiners or a holographic/diffractive optical element.
The combined beam is focused on the multilayer optical disk using suitable axially dispersing optics, so that a multiplicity of axially displaced foci along the spinning axis of the disks are obtained, depending on the wavelengths of the various lasers source.
The dispersing optics includes an on-axis diffractive lens or hybrid diffractive-refractive optical element.
The beam from each source of a different wavelength, such as diode laser beams, is focused on a corresponding optical disk surface and is reflected back from the surface to produce a reflected beam which includes information related to the zone of the optical disk surface being read
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Optical Systems 
