15-06-2012, 03:44 PM
Holographic memory
[attachment=24597]
ABSTRACT
Holographic memory is a technique that can store information at high density inside crystals Holographic memory is developing technology that has promised to revolutionalise the storage systems. It can store data up to 1Tb in a sugar cube sized crystal. Data from more than 1000 CDs can fit into a holographic memory System. Holographic storage has the potential to become the next generation of storage media Conventional memories use only the surface to store the data. But holographic data storage systems use the volume to store data. It has more advantages than conventional storage systems. It is based on the principle of holography
INTRODUCTION
Scientist J. V. Heerden came up with this idea in 1960. With the rapid advances in computer technology, the demands of more storage and faster transfer rates are pushing modern magnetic and optical based storage solutions to the limit. Every bit of performance is required for these unbelievable speeds and capacities, and as their rates slowly reach a plateau, next possible revolution in data storage is Holography.
Holographic data storage is a volumetric approach which, with three-dimensional recording and parallel data readout, holographic memories can outperform existing optical storage techniques. Unlike other technologies, that record one data bit at a time, holography allows a million bits of data to be written and read in parallel with a single flash of light. Holograms can theoretically store equal to one bit per cubic block the size of the wavelength of light in writing.
In its basic form, a hologram is the photographic record of the spatial interference pattern created by the mixing of two coherent laser beams. One of the beams usually carries spatial information and is labeled the "object" beam. The other is distinguished by its particular direction of travel and is labeled the "reference" beam. Illuminating the recorded hologram with the reference beam will yield or reconstruct the object beam and vice versa. As the holographic material becomes thicker, the reconstruction becomes very sensitive to the particular angle of incidence of the reference beam, which allows multiple objects to be recorded in the same volume and accessed independently by using an appropriate set of associated reference beams. Such holograms would be recorded sequentially, each object beam illuminating the holographic material simultaneously with its unique reference beam.
Working of HDDS
Recording Data On Medium
Creating holograms is achieved by means of two coherent beams of light split from one laser source, one being the reference beam and the other signal beam. When both these beams interfere with one another, a resulting interference pattern is formed which encompasses the pattern both in amplitude and phase in formation of the two beams. When an appropriate photorefractive material is placed at the point of interference, the interference patterns are recorded inside the material. The beam's angle is crucial, and it can't vary by more than a fraction of a degree. This apparent flaw in the recording process is actually an asset. It's how holographic storage achieves its high data densities.
Multiplexing
Once one can store a page of bits in a hologram, an interface to a computer can be made. The problem arises however, that storing only one page of bits is not beneficial.
Fortunately, the properties of holograms provide a unique solution to this dilemma. Unlike magnetic storage mechanisms which store data on their surfaces, holographic memories store information throughout their volume. After a page of data is recorded in the hologram, a small modification to the source beam before it re enters the hologram will record another page of data in the same volume. This method of storing multiple pages of data in the hologram is called multiplexing. The thicker the volume becomes smaller the modifications to the source beam can be.
Implementation
A holographic data storage system consists of a recording medium, an optical recording system, a photo detector array. A beam of coherent light is split into a reference beam and a signal beam which are used to record a hologram into the recording medium . The recording medium is usually a photorefractive crystal.
[attachment=24597]
ABSTRACT
Holographic memory is a technique that can store information at high density inside crystals Holographic memory is developing technology that has promised to revolutionalise the storage systems. It can store data up to 1Tb in a sugar cube sized crystal. Data from more than 1000 CDs can fit into a holographic memory System. Holographic storage has the potential to become the next generation of storage media Conventional memories use only the surface to store the data. But holographic data storage systems use the volume to store data. It has more advantages than conventional storage systems. It is based on the principle of holography
INTRODUCTION
Scientist J. V. Heerden came up with this idea in 1960. With the rapid advances in computer technology, the demands of more storage and faster transfer rates are pushing modern magnetic and optical based storage solutions to the limit. Every bit of performance is required for these unbelievable speeds and capacities, and as their rates slowly reach a plateau, next possible revolution in data storage is Holography.
Holographic data storage is a volumetric approach which, with three-dimensional recording and parallel data readout, holographic memories can outperform existing optical storage techniques. Unlike other technologies, that record one data bit at a time, holography allows a million bits of data to be written and read in parallel with a single flash of light. Holograms can theoretically store equal to one bit per cubic block the size of the wavelength of light in writing.
In its basic form, a hologram is the photographic record of the spatial interference pattern created by the mixing of two coherent laser beams. One of the beams usually carries spatial information and is labeled the "object" beam. The other is distinguished by its particular direction of travel and is labeled the "reference" beam. Illuminating the recorded hologram with the reference beam will yield or reconstruct the object beam and vice versa. As the holographic material becomes thicker, the reconstruction becomes very sensitive to the particular angle of incidence of the reference beam, which allows multiple objects to be recorded in the same volume and accessed independently by using an appropriate set of associated reference beams. Such holograms would be recorded sequentially, each object beam illuminating the holographic material simultaneously with its unique reference beam.
Working of HDDS
Recording Data On Medium
Creating holograms is achieved by means of two coherent beams of light split from one laser source, one being the reference beam and the other signal beam. When both these beams interfere with one another, a resulting interference pattern is formed which encompasses the pattern both in amplitude and phase in formation of the two beams. When an appropriate photorefractive material is placed at the point of interference, the interference patterns are recorded inside the material. The beam's angle is crucial, and it can't vary by more than a fraction of a degree. This apparent flaw in the recording process is actually an asset. It's how holographic storage achieves its high data densities.
Multiplexing
Once one can store a page of bits in a hologram, an interface to a computer can be made. The problem arises however, that storing only one page of bits is not beneficial.
Fortunately, the properties of holograms provide a unique solution to this dilemma. Unlike magnetic storage mechanisms which store data on their surfaces, holographic memories store information throughout their volume. After a page of data is recorded in the hologram, a small modification to the source beam before it re enters the hologram will record another page of data in the same volume. This method of storing multiple pages of data in the hologram is called multiplexing. The thicker the volume becomes smaller the modifications to the source beam can be.
Implementation
A holographic data storage system consists of a recording medium, an optical recording system, a photo detector array. A beam of coherent light is split into a reference beam and a signal beam which are used to record a hologram into the recording medium . The recording medium is usually a photorefractive crystal.