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Seminar Report On Holographic data storage system (HDSS)

BY

A.Arjun Reddy (arjun_red555@yahoo.co.in)

AND A.Santosh (santosh0511@gmail.com) 3/4 IT 2nd SEMISTER

DEPARTMENT OF INFORMATION TECHNOLOGY SREENIDHI INSTITUTE OF SCIENCE AND TECHNOLOGY Affliated to JNTU-University Ghatkesar Hyderbad

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CONTENTS

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1 ABSTRACT

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2 INTRODUCTION...

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3 WORKING OF HDDS 3.1 RECORDING DATA ON MEDIUM 3.2 READING DATA FROM HOLOGRAM

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4 IMPLEMENTATION

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5 ADVANTAGES

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6 DISADVANTAGES

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7 POSSIBLE APPLICATIONS

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8 CONCLUSION

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9 REFERENCES.....................................................................10

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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 This paper provides a description of Holographic data storage system (HDSS), a three dimensional data storage system which has a fundamental advantage over conventional read/write memory systems. A brief overview of properties of holograms will be presented first. Applications to computer systems are then covered, with the future of holographic memory presented as a conclusion.

ADVANTAGES OF HDDS1 Personal computer with a holographic technology platform (HoloPCs) will be able to access data more rapidly and in a qualitatively different manner than conventional PCs. 2 Two-dimensional data saving systems such as CDs and DVDs record and retrieve files in a serial fashion -- one bit at a time. Holographic data systems retain and retrieve data in parallel, a total (million-bit) page of files at a time. 3 The interface of holography and robotics may make "holobots" that learn through creative identification of useful patterns in big quantities of files. 4 Eventually, optical neural networks may be possible using holographic research

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INTRODUCTIONEach time you watch a fast-paced DVD movie or pull down a piece of information from the Internet or even access the ATM at the corner of your street, you are actually tapping into large repositories of digital information. The hard disk, the mainstay of personal and corporate storage, has faithfully obeyed the exponential law. This has happened largely due to increases in aerial density, that is, how many bits are crammed into a square inch. This paper provides a description of Holographic data storage system (HDSS), a three dimensional data storage system which has a fundamental advantage over conventional read/write The first step in understanding holographic memory is to understand what "holographic" means. Holography is a method of recording patterns of light to produce a threedimensional object. The recorded patterns of light are called hologram memory systems. Holographic memory is a technique that can store information at high density inside crystals or photopolymers. As current storage techniques such as DVD reach the upper limit of possible data density (due to the diffraction limited size of the writing beams), holographic storage has the potential to become the next generation of storage media. The advantage of this type of data storage is that the volume of the recording media is used instead of just the surface.

WORKING OF HDSS

RECORDING DATA ON MEDIUMCreating holograms is achieved by means of two coherent beams of light split from one laser source, one being the reference beam and the other the signal beam. When both these

-5beams interfere with one another, a resulting interference pattern is formed which encompasses the pattern both in amplitude and phase information 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. By changing either the angle of the reference beam or its frequency, you can write additional data pages in to the same volume of crystal. The dynamic range of the medium determines how many pages it can hold reliably.

FIG :

HOW DATA IS RECORDED ON A MEDIU

READING DATA FROM HOLOGRAM

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FIG: HOW DATA IS READ FROM HOLOGRAM

When the reference beam illuminates the material in the absence of the signal beam, the hologram causes the light to be diffracted in the same direction of the initial signal beam and all the information of the original signal beam is reconstructed

MULTIPLEXINGOnce 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 whole volume. After a page of data is recorded in the hologram, a small modification to the source beam before it reenters 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.

. IMPLEMENTATIONA 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 photo refractive crystal A hologram is simply the three-dimensional interference pattern of the intersection of the reference and signal beams are perpendicular to each other. This interference pattern is imprinted into the crystal as regions of positive and negative charges. To retrieve the stored hologram, a beam of light that has the same wavelength and angle of incidence as the reference beam is sent into the crystal and the resulting diffraction pattern is used to reconstruct the pattern of the signal beam. Many different holograms may be stored in the same crystal volume by changing the angle of incidence of reference beam

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FIG INPLEMENTATION OF HDD

The most common holographic recording system uses laser light, a beam splitter to divide the laser light into reference beam and signal beam, various lenses and mirrors to redirect the light, a photo reactive crystal, and an array of photo detectors around the crystal to receive the holographic data. To record a hologram, a beam laser light is split into two beams by a mirror. These two beams then become the reference and signal beams. The signal beam interacts with an object and the light that is reflected by the object intersects the reference beam at right angles. The resulting interference pattern contains all the information necessary to recreate the image of the object after suitable processing. The interference pattern is recorded on to a photo reactive material and may be retrieved at a latter time by using a beam that is identical to the reference beam. This is possible because the hologram has the property that if it is illuminated by either of the beams used to record it, the hologram causes light to be diffracted in the direction of the second beam that was used to record it, there by recreating the reflected image of the object if the reference beam was used to illuminate the hologram. So, the reflected must be

-8transformed into a real image with mirrors and lenses that can be sent to the laser detector array.

ADVANTAGES

With three-dimensional recording and parallel data readout, holographic memories can outperform existing optical storage techniques. In contrast to the currently available storage strategies, holographic mass memory simultaneously offers high data capacity and short data access time (Storage capacity of about 1TB/cc and data transfer rate of 1 billion bits/second). Holographic data storage has the unique ability to locate similar features stored within a crystal instantly. A data pattern projected into a crystal from the top searches thousands of stored holograms in parallel. The holograms diffract the incoming light out of the side of the crystal, with the brightest outgoing beams identifying the address of the data that most closely resemble the input pattern. This parallel search capability is an inherent property of holographic data storage and allows a database to be searched by content. Because the interference patterns are spread uniformly throughout the material, it endows holographic storage with another useful capability: high reliability. While a defect in the medium for disk or tape storage might garble critical data, a defect in a holographic medium doesn't wipe out information. Instead, it only makes the hologram dimmer. No rotation of medium is required as in the case of other storage devices. It can reduce threat of piracy since holograms cant be easily replicated.

DISADVANTAGES OF HDDS

Manufacturing cost HDSS is very high and there is a lack of availability of resources which

-9are needed to produce HDSS. However, all the holograms appear dimmer because their patterns must share the material's finite dynamic range. In other words, the additional holograms alter a material that can support only a fixed amount of change. Ultimately, the images become so dim that noise creeps into the read-out operation, thus limiting the material's storage capacity. A difficulty with the HDSS technology had been the destructive readout. The reilluminated reference beam used to retrieve the recorded information, also excites the donor electrons and disturbs the equilibrium of the space charge field in a manner that produces a gradual erasure of the recording. In the past, this has limited the number of reads that can be made before the signal-to -noise ratio becomes too low. Moreover, writes in the same fashion can degrade previous writes in the same region of the medium. This restricts the ability to use the three-dimensional capacity of a photorefractive for recording anglemultiplexed holograms. You would be unable to locate the data if theres an error of even a thousandth of an inch.-

POSSIBLE APPLICATIONSThere are many possible applications of holographic memory. Holographic memory systems can potentially provide the high speed transfers and large volumes of future computer system. One possible application is data mining. Data mining is the processes of finding patterns in large amounts of data. Data mining is used greatly in large databases which hold possible patterns which cant be distinguished by human eyes due to the vast amount of data. Some current computer system implement data mining, but the mass amount of storage required is pushing the limits of current data storage systems. The many advances in access times and data storage capacity that holographic memory provides could exceed conventional storage and speedup data mining considerably. This would result in more located patterns in a shorter amount of time. Another possible application of holographic memory is in petaflop computing. A petaflop is a thousand trillion floating point operations per second. The fast access extremely large

- 10 amounts of data provided by holographic memory could be utilized in petaflop architecture. Clearly advances are needed to in more than memory systems, but the theoretical schematics do exist for such a machine. Optical storage such as holographic memory provides a viable solution to the extreme amount of data which is required for a petaflop computing.

CONCLUSIONThe future of HOLOGRAPHIC DATA STORAGE SYSYEM is very promising. The page access of data that HDSS creates will provide a window into next generation computing by adding another dimension to stored data. Finding holograms in personal computers might be a bit longer off, however. The large cost of high-tech optical equipment would make small-scale systems implemented with HDSS impractical. It will most likely be used in next generation supercomputers where cost is not as much of an issue. Current magnetic storage devices remain far more cost effective than any other medium on the market. As computer system evolve, it is, not unreasonable to believe that magnetic storage will continue to do so. As mentioned earlier, however, these improvements are not made on the conceptual level. The current storage in a personal computer operates on the same principles used in the first magnetic data storage devices. The parallel nature of HDSS has many potential gains on serial storage methods. However, many advances in optical technology and photosensitive materials need to be made before we find holograms in our computer systems.

REFERENCE.......www.holopc.com ........www.wikeipedia.com .........www.engeeniringseminars.com ..........www.computer.howstuffworks.com

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The Herald - the herald is not one of the steps, but an archetype. He is usually the one who introduces the next step in the hero's journey. In Star Wars the Herald is R2D2 a little droid with a holographic message on his hard disc.

2. The Call to Adventure

In Star Wars, the holographic message by Princess Leia is the Call to Adventure. 'Help me,' she says, 'you're my only hope.' The Call usually asks the hero to leave his world and go on a quest to save an object or person of great value. Lord of the Rings seems to contradict his, because Frodo's goal is to destroy the ring, but think about it. If he succeeds then he will essentially save Middle Earth.