22-08-2013, 04:55 PM
SEMINAR REPORT ON HOLOGRAPHIC VERSATILE DISK
[attachment=57377]
ABSTRACT
The Information Age has led to an explosion of information available to users,while current storage needs are being met, storage technologies must continue to improve in order to keep pace with the rapidly increasing demand.However, conventional data storage technologies ,where individual bits are stored as distinct magnetic or optical changes on the surface of a recording medium, are approaching physical limits. Storing information throughout the volume of a medium — not just on its surface —offers an intriguing high-capacity alternative.
Holographic data storage is a volumetric approach which , although conceived decades ago, has made recent progress toward practicality with the appearance of lower- cost enabling technologies , significant results from longstanding research efforts, and progress in holographic recording materials. Holographic versatile disc (HVD) is a holographic storage format capable of storing far more data than DVD.
Prototype HVD devices have been created with a capacity of 3.9 terabytes (TB) and a transfer rate of 1 gigabit per second (1 Gbps). At that capacity, an HVD could store as much information as 830 DVDs or 160 Blu-ray discs.
INTRODUCTION
An HVD (Holographic Versatile Disc), a holographic storage media, is an advanced optical disk that's presently in the development stage. Polaroid scientist J. van Heerden was the first to come up with the idea for holographic three-dimensional storage in 1960. An HVD would be a successor to today's Blu-ray and HD-DVD technologies. It can transfer data at the rate of 1 Gigabit per second. The technology permits over 10 kilobits of data tobe written and read in parallel with a single flash. The disk will store upto 3.9 terabyte (TB) of data on a single optical disk.
Holographic data storage, a potential next generation storage technology, offers both high storage density and fast readout rate. In this article, I discuss the physical origin of these attractive technology features, and the components and engineering required to realize them. The strengths and weaknesses of available write-once and read-writeable storage media are discussed, including the development issues of achieving non-volatile readout from read-write media. Systems issues such as the major noise sources and avenues for defeating or finessing them are detailed, including the potentials and pitfalls of phase- conjugate readout and holographic storage on spinning media.
BRIEF HISTORY
Although holography was conceived in the late 1940s, it was not considered a potential storage technology until the development of the laser in the 1960s. The resulting rapid development of holography for displaying 3-D images led researchers to realize that holograms could also store data at a volumetric density of as much as 1/ A3 where A, is the wave-length of the light beam used. Since each data page is retrieved by an array of photo detectors in parallel, rather than bit-by-bit, the holographic scheme promises fast readout rates as well as high density.If a thousand holograms, each containing a million pixels, could be retrieved every second, for instance, then the output data rate would reach 1 Gigabit per second.
Despite this attractive potential and fairly impressive early progress research into holographic data storage died out in the mid-1970s because suitable devices for the input and output of large pixelated 2-D data pages were just not available. In the early 1990s, interest in volume-holographic data storage was rekindled by the availability of devices that could display and detect 2-D pages, including charge coupled devices (CCD), complementary metal-oxide semiconductor (CMOS) detector chips and small liquid-crystal panels. The wide availability of these devices was made possible by the commercial success of hand-held camcorders, digital cameras, and video projectors.
COLLINEAR HOLOGRAPHY
HVD uses a technology called 'collinear holography,' in which two laser rays, one blue- green and one red, are collimated into a single beam. The role of the blue-green laser is to read the data encoded in the form of laser interference fringes from the holographic layer on the top, while the red laser serves the purpose of a reference beam and also to read the servo info from the aluminum layer - like in normal CDs - near the bottom of the disk.
The servo info is meant to monitor the coordinates of the read head above the disk (this is similar to the track, head and sector information on a normal hard disk drive).
Fig shows the two laser collinear Fig shows the interference holography technique pattern stored on the disc.
DATA STORAGE
RECORDING DATA
Holographic data storage works on the principle of holography. In holographic data storage an entire page of information is stored at once as an optical interference pattern within a thick, photosensitive optical material.This is done by intersecting two coherent laser beams within the storage material. The first, called the object beam, contains the information to be stored; the second, called the reference beam, is designed to be simple to reproduce. The resulting optical interference pattern causes chemical and/or physical changes in the photosensitive medium. A replica of the interference pattern is stored as a change in the absorption, refractive index, or thickness of the photosensitive medium. Illuminating the stored grating with the reference wave reconstructs the object wave. Light from a single laser beam is divided into two separate beams, a reference beam and an object or signal beam; a spatial light modulator is used to encode the object beam with the data for storage. An optical inference pattern results from the crossing of the beams' paths, creating a chemical and/or physical change in the photosensitive medium; the resulting data is represented in an optical pattern of dark and light pixels. By adjusting the reference beam angle, wavelength, or media position, a multitude of holograms (theoretically, several thousand) can be stored on a single volume. The theoretical limits for the storage density of this technique are approximately tens of terabits (1 terabyte =1,000 gigabytes) per cubic centimeter.
[attachment=57377]
ABSTRACT
The Information Age has led to an explosion of information available to users,while current storage needs are being met, storage technologies must continue to improve in order to keep pace with the rapidly increasing demand.However, conventional data storage technologies ,where individual bits are stored as distinct magnetic or optical changes on the surface of a recording medium, are approaching physical limits. Storing information throughout the volume of a medium — not just on its surface —offers an intriguing high-capacity alternative.
Holographic data storage is a volumetric approach which , although conceived decades ago, has made recent progress toward practicality with the appearance of lower- cost enabling technologies , significant results from longstanding research efforts, and progress in holographic recording materials. Holographic versatile disc (HVD) is a holographic storage format capable of storing far more data than DVD.
Prototype HVD devices have been created with a capacity of 3.9 terabytes (TB) and a transfer rate of 1 gigabit per second (1 Gbps). At that capacity, an HVD could store as much information as 830 DVDs or 160 Blu-ray discs.
INTRODUCTION
An HVD (Holographic Versatile Disc), a holographic storage media, is an advanced optical disk that's presently in the development stage. Polaroid scientist J. van Heerden was the first to come up with the idea for holographic three-dimensional storage in 1960. An HVD would be a successor to today's Blu-ray and HD-DVD technologies. It can transfer data at the rate of 1 Gigabit per second. The technology permits over 10 kilobits of data tobe written and read in parallel with a single flash. The disk will store upto 3.9 terabyte (TB) of data on a single optical disk.
Holographic data storage, a potential next generation storage technology, offers both high storage density and fast readout rate. In this article, I discuss the physical origin of these attractive technology features, and the components and engineering required to realize them. The strengths and weaknesses of available write-once and read-writeable storage media are discussed, including the development issues of achieving non-volatile readout from read-write media. Systems issues such as the major noise sources and avenues for defeating or finessing them are detailed, including the potentials and pitfalls of phase- conjugate readout and holographic storage on spinning media.
BRIEF HISTORY
Although holography was conceived in the late 1940s, it was not considered a potential storage technology until the development of the laser in the 1960s. The resulting rapid development of holography for displaying 3-D images led researchers to realize that holograms could also store data at a volumetric density of as much as 1/ A3 where A, is the wave-length of the light beam used. Since each data page is retrieved by an array of photo detectors in parallel, rather than bit-by-bit, the holographic scheme promises fast readout rates as well as high density.If a thousand holograms, each containing a million pixels, could be retrieved every second, for instance, then the output data rate would reach 1 Gigabit per second.
Despite this attractive potential and fairly impressive early progress research into holographic data storage died out in the mid-1970s because suitable devices for the input and output of large pixelated 2-D data pages were just not available. In the early 1990s, interest in volume-holographic data storage was rekindled by the availability of devices that could display and detect 2-D pages, including charge coupled devices (CCD), complementary metal-oxide semiconductor (CMOS) detector chips and small liquid-crystal panels. The wide availability of these devices was made possible by the commercial success of hand-held camcorders, digital cameras, and video projectors.
COLLINEAR HOLOGRAPHY
HVD uses a technology called 'collinear holography,' in which two laser rays, one blue- green and one red, are collimated into a single beam. The role of the blue-green laser is to read the data encoded in the form of laser interference fringes from the holographic layer on the top, while the red laser serves the purpose of a reference beam and also to read the servo info from the aluminum layer - like in normal CDs - near the bottom of the disk.
The servo info is meant to monitor the coordinates of the read head above the disk (this is similar to the track, head and sector information on a normal hard disk drive).
Fig shows the two laser collinear Fig shows the interference holography technique pattern stored on the disc.
DATA STORAGE
RECORDING DATA
Holographic data storage works on the principle of holography. In holographic data storage an entire page of information is stored at once as an optical interference pattern within a thick, photosensitive optical material.This is done by intersecting two coherent laser beams within the storage material. The first, called the object beam, contains the information to be stored; the second, called the reference beam, is designed to be simple to reproduce. The resulting optical interference pattern causes chemical and/or physical changes in the photosensitive medium. A replica of the interference pattern is stored as a change in the absorption, refractive index, or thickness of the photosensitive medium. Illuminating the stored grating with the reference wave reconstructs the object wave. Light from a single laser beam is divided into two separate beams, a reference beam and an object or signal beam; a spatial light modulator is used to encode the object beam with the data for storage. An optical inference pattern results from the crossing of the beams' paths, creating a chemical and/or physical change in the photosensitive medium; the resulting data is represented in an optical pattern of dark and light pixels. By adjusting the reference beam angle, wavelength, or media position, a multitude of holograms (theoretically, several thousand) can be stored on a single volume. The theoretical limits for the storage density of this technique are approximately tens of terabits (1 terabyte =1,000 gigabytes) per cubic centimeter.