Devices that use light to store and read data have been the backbone of data storage for nearly two decades. These conventional storage mediums meet today's storage needs. However, storage technologies have to evolve to keep in pace with increasing consumer demand on the one hand and technological advancements on the other. CDs, DVDs and magnetic storage all store bits of information on the surface of a recording medium. In order to increase storage capabilities, scientists have been working on a new optical storage method, called holographic memory that will go beneath the surface and use the volume of the recording medium for storage, instead of only the surface area. Three-dimensional data storage will be able to store more information in a smaller space and offer faster data transfer times.
Holography breaks through the density limits of conventional storage. Unlike other technologies that record one data bit at a time, holography records and reads over a million bits of data with a single flash of light. This enables transfer rates significantly higher than current optical storage devices. High storage densities and fast transfer rates, combined with durable, reliable, low cost media, make holography poised to become a compelling choice for next-generation storage.
Holographic storage is the solution to the storage demands of individuals and organizations. Newly developed Holographic Versatile Discs offer potentially 20 times the storage data of older mediums, providing consumers significant advantages.
The Computer world is so dynamic that even keen observers may not be able to keep up with the pace of evolution.
There is a joke about personal computers that has been around almost as long as the devices have been on the market: You buy a new computer, take it home and just as you finish unpacking it you see an advertisement for a new computer that makes yours obsolete. If you're the kind of person who demands to have the fastest, most powerful machines with extensive storage and memory capacity, it seems like you're destined for frustration and a lot of trips to the computer store.
While the joke is obviously an exaggeration, it is not that far off the mark. Even one of today's modest personal computers has more processing power and storage space than the famous Cray-1 supercomputer. In 1976, the Cray-1 was state-of-the-art: it could process 160 million floating-point operations per second (flops) and had 8 megabytes (MB) of memory.
Today, many personal computers can perform more than 10 times that number of floating-point operations in a second and have 100 times the amount of memory.
If you were to chart the evolution of the computer in terms of processing power, you would see that progress has been exponential. The man who first made this famous observation is Gordon Moore, a co-founder of the microprocessor company Intel. Computer scientists, electrical engineers, manufacturers and journalists extrapolated Moore's Law from his original observation. In general, most people interpret Moore's Law to mean the number of transistors on a 1-inch (2.5 centimeter) diameter of silicon doubles every x number of months.
Over the decades, there has been a constant inverse proportionality between Processor size and speed/ Storage capacity of Computers. While Processor size has been leaning more and more towards the micro scale or even less, Speed and processing capability is in the giga scale and Storage is from giga scale upwards.
This, invariably, has influenced the overall size of general computers. Also, demand for storage capacity and performance has risen sharply, as microprocessors have grown faster, software applications have become more resource intensive, and network computing has become more pervasive. Attempts to harness processing power and offer users more features have made the typical new software application require vastly more storage space than earlier versions. On personal computers, storage needs have further evolved and multiplied because of expanding multimedia features and content, such as DVD movies and downloadable music on the Internet. Meanwhile, corporate systems have had to cope with escalating storage and processing needs from internal users, as well as from the Internet.
Devices that use light to store and read data have been the backbone of data storage for nearly two decades. Compact discs revolutionized data storage in the early 1980s, allowing multi-megabytes of data to be stored on a disc that has a diameter of a mere 12 centimeters and a thickness of about 1.2 millimeters. In 1997, an improved version of the CD, called a digital versatile disc (DVD), was released, which enabled the storage of full-length movies on a single disc.
Though Moore’s Law is still relevant today, it will, invariably, fizzle out into irrelevance considering the technological advances the Computer World is experiencing daily. The aim of Computer manufacturers is to produce smaller sized Computers with extremely fast Processors and extensively large Storage capabilities. However, if miniaturization must be sustained, there is the need for a more concise yet substantial storage mechanism that can fit into the ever reducing size of the modern day Computer.
Justification of study
Holography in itself is not a new concept; it has been around for decades. However, because it is dependent on other technologies, it has since only evolved or re – evolved together with these other technologies. Holographic data storage is not possible without LASER; it wasn’t until about fifteen years after holograph was discovered before LASER was discovered. Consequent upon all the technologies upon which holograph is dependent, the emergence of holography has been hitherto stunted.
Indeed, the theoretical promise of holographic storage has been talked about for 40 years. But advances in smaller and cheaper lasers, digital cameras, projector technologies, and optical recording materials have finally pushed the technology to the verge of the market. And the ability to cram exponentially more bits into infinitesimal spaces could open up a whole new realm of applications.
It has been something of a digital philosopher’s stone since the ’60s, promising infinite storage and massive data rates. When a holographic storage prototype was finally demonstrated at NAB 2005 by InPhase Technologies, many couldn’t believe that we might actually be standing on the cusp of a storage renaissance.
In 2010, though, with no further public demonstrations, $100 million spent, over ten years of research and development, and commercial viability remaining elusive, InPhase ran out of money and shut up shop. For many storage nerds, it was the end of a dream. Well, good news: InPhase’s assets was bought up by a company called HVault, that demonstrated its holographic storage tech at NAB 2012 in Las Vegas. Better yet, HVault launched in spring of 2012.
Currently, HVault provides complete holographic storage systems for any size archive. All HVault storage systems are designed to plug in to existing network architectures with no disruption to existing workflows.
Data storage has been a fundamental part of computing from the beginning. The technology for data storage has been evolving alongside other areas of computing technology.
The ability to store and process information in new ways has been essential to humankind's progress. From the early Egyptian papyrus through the Gutenberg press, the Dewey decimal system and eventually, holographic technology, information storage has been the catalyst for increasingly complex technological, scientific and societal systems. Modern science is inextricably bound to information processing with which it exists in a form of symbiosis. Scientific advances have enabled the storage, retrieval and processing of ever more information, which in turn, helped generate the insights needed for further advances.
New Multimedia applications, and the normal day to day data operations are placing new demands on storage systems (Multimedia refers to the integration of text, audio, still images, video, and graphics into an easily manipulated digital format). These kinds of documents require 10 to 1000 times the storage capacity required by conventional documents. Multimedia programs eat up a large amount of storage space. Each second of full motion, full screen video requires 30 frames of video information at the rate of almost a megabyte (MB) of computer data per frame. That is about 30 MB of information per second, or 1.8 gigabyte (GB) per minute. This amount is not generally available, particularly in portable systems, which is the most promising sector in this industry following the trend toward miniaturization and more compact computers.
Background to the Survey
Until now, multimedia storage has been achieved using the technique called "compression", which consists of the coding of data in fewer bits that is normally done to save storage space or transmission time. Specialized software automatically compresses and decompresses data. However the key to high-quality multimedia playback is the sustained throughput (uninterrupted transfer) of information. Without it, frames are lost during capture and playback. The result is poor production quality in the form of blips, lost frames and flicker (Barr, 1993).
For this and other reasons, multimedia producers and developers have learned to develop a healthy respect for computer storage technology. Storage is seen by many in the industry as the critical enabling technology for many new multimedia applications and to address its rapidly increasing requirements is the key to bring forward this new technology. Currently, this storage is provided by magnetic and optical technologies, and despite fantastic advances in these technologies, physical limitations are involved in getting data on and off of the conventional (mechanical) rotating devices. For example, disk based storage uses moving parts that poop out at a certain speed (Gibbs, 1993), and further progress in CD-ROM technology faces a fundamental limit: the pits that encode information on the surface of a compact disk can be no smaller than the wavelength of the laser light used to read them (Parish, 1990).
Evidently, the next giant leap in computer data storage capacity will have to come from elsewhere. In fact, the increased demand for significantly more storage capacity coupled with the development of the wide variety of applications have considerably taxed the ability of these storage systems. While this gap is temporarily hindering the emergence of multimedia, there is a rapidly growing pressure for such technology. The opinion of many industry leaders is that, whoever delivers a solution to the current storage capacity problem will dominate the information storage market of the future.
Efficient multimedia systems require high density, interchangeable media for the majority of their applications. These applications vary from the initial loading of software, to multimedia presentations, to simple back up of files located on the device.
As these other areas of technology have developed, the need for bigger and faster storage has been evident. To meet the need for better storage, new technologies are constantly being developed as the old technology reaches its physical limits and becomes outdated. Currently there are several new technologies being researched as possible replacements for current storage devices.
The general characteristics of storage devices for the multimedia product environment are:
Store information in a form that can be easily manipulated by electronics.
Safely store huge amounts of information, typically, one to more than a thousand gigabits so that it can be preserved indefinitely as archives.
Any part of the stored information can be read out or changed at any time with the shortest possible delay which, particularly for the fleeting intermediary data occurring in processing, is typically one millisecond or less.
Low power consumption (1 watt average).
Low cost per megabyte of memory (Less than one dollar per MB)
Information is said to have been written in a chosen medium if its physical or chemical state is altered under the influence of the signal (or writing beam) energy. The altered state in a storage medium is brought about by making proper use of one or more of its characteristic properties (thermal, chemical, electrical, magnetic, elastic, optical, etc.). Reading of the stored information is accomplished by sensing the altered state using an appropriate technique, and erasing of information is achieved using such means as electrical, magnetic or optical, either alone or in some suitable combination (Tapscott, 1993).
Recent years have witnessed a significant increase in electronic management of information. In particular, many types of information that traditionally were considered to be analog, such as images and sound, are now processed and utilized in digital form. This advancement comes with tremendous opportunities and challenges for information systems to better meet information users’ needs to manipulate multimedia information in a natural and effective manner. Many industries, among which is multimedia, are eagerly looking for new alternatives to their current storage systems, as their databases, and storage requirements are growing larger and larger.
Magnetic and optical systems have long dominated the storage market. However an increasing demand for significantly more storage capacity coupled with the development of a wide variety of applications have taxed the ability of these storage systems. And as the requirements on these systems continue to grow, the limits of current technology will eventually be reached. One solution as identified by researchers and industry leaders is a holographic storage system. This system in contrast to conventional magnetic and optical recording requires the unique integration of many different technologies as opposed to one dominant technology. By combining these technologies, it is anticipated that the resulting storage system would be both original and competitive in performance, size, and cost.
Holographic data storage technology is a relatively new type of data storage offering compact storage capacity; higher data transfers rates and significantly longer archival life. The technology is based on the recording and reading of data in the form of holograms. Holographic data storage has been discussed since the 1960s, but has only recently become a commercially viable technology.
The terms holograms and holography were coined by Dennis Gabor (a Hungarian-born physicist and Nobel Prize winner, also known as the father of holography) in 1947. "Holos" stands in Greek for "total, complete"; "gramma" means letter and writing. It has the same roots as "graphein" (to write). In ancient Greece, however, the letter was also used as a number or system for the measurement of distinguishable unities, like in the word "kilogram", which does not mean writing with weight but the unity formed by one thousand grams. So if "gram" designates the unity and "holos", the total, the word" hologram" means the unity of the whole as well as the wholeness of the unity.
While photography as we know it today was invented by Nitpce as a culmination of centuries of research in that direction, holography, as many other inventions in the twentieth century, was the by-product of a search for something else. Namely, a method for improving the quality of images recorded on an electronic microscope. As opposed to photography, holography did not come as a consequence of centuries of perfectibility. Dennis Gabor, its inventor, needed in 1947 what was to be later called a laser to make three-dimensional holograms, but he invented holography almost fifteen years ahead of the appearance of the first laser which two engineers from the University of Michigan, namely Emmett Leith and Juris Upatnieks discovered in the early sixties. These two developed a new device which produced a three dimensional image of an object (Heckman, 1986). Building on the discoveries of the "father of holography", they produced the diffuse-light hologram. They were eerie, lifelike, three-dimensional pictures. One of the most startling characteristics of the holograms was that if you smashed the holographic plate, or the negative, every piece was capable of reconstructing the whole scene. Although an image from the tiniest fragments can fade and lose detail, the image itself is still whole, whether the piece came from the middle, bottom or top of the hologram (Jeong, 1975). When the first three-dimensional holograms were made, the technique was labeled "a solution in
search of a problem" by the press.
For the purpose of examining some characteristics of holography by contrast, let us expose some of the other basic differences between holography and photography.
First of all, we need to understand that, as opposed to the photograph, the hologram is not a picture and holography is not primarily a picture-making technique. A hologram does not bear an image at all. What it actually does is just to perform the function of a lens, and only diffracts light in a particular way. In this sense, holograms are optical elements, not pictures. They perform optical functions rather than bear an image, and they are not extensions of photographs but a new way of recording, storing and retrieving optical information (information carried by light waves).
A photograph is basically the recording of the differing intensities of the light reflected by the object and imaged by a lens. The light is incoherent, therefore, there are many different wavelengths of light reflecting form the object and even the light of the same wavelength is out of phase (Outwater, 1995). Your emulsion will react to the light image focused by the lens and the chemical change of the silver halide molecules will result from the photon bombardment. There is a point to point correspondence between the object and the emulsion. Any object to be recorded can be thought of as the sum of billions of points on the object which are reflecting more or less light. The lens of the camera focuses each object point to a corresponding point on the film and there it exposes a proportional amount of silver halide. Thus, your record is of the intensity differences on the object which form a pattern that one may ultimately recognize as the object photographed.
In holography, light waves and silver halide emulsion are used, but beyond that, the comparison ceases, as holography uses a vastly different light source: Laser light.
Laser light differs drastically from all other light sources, man-made or natural, in one basic way which leads to several startling characteristics. Laser light can be coherent light. Ideally this means that the light being emitted by the laser is of the same wavelength and is in phase.
Gabor's theory was originally intended to increase the resolving power of electron microscopes (Jeong, 1975). The Nobel Prize physicist proved his theory not with an electron beam but with a light (non-coherent) light beam. The result was the first hologram ever made. The early holograms were legible but were plagued with many imperfections because Gabor didn't have the correct light source to make crisp, clear holograms as we can today. This is one of the reasons his discovery wasn't fully appreciated until the 1960's when the first laser was produced, since holograms could be realized only using coherent light. Since then, holography has become one of the newest and most intriguing of the many techniques with which technology has been concerned, and in many peoples' opinion now seems to likely become extremely helpful in many human endeavors, and will open a broad new horizon for the future (Glantz, 1994). The simplest description of holography is three dimensional recording with lasers. In other words, holography is the technology of recording wave-front (light wave) information and producing reconstructed wave-fronts from those recordings. The record of the wave-front information is called a hologram. Any propagating wave-front phenomenon such as microwaves or acoustic waves is a candidate for application of the principles of holography (Outwater, 1995).
How Holographic Storage Works
Holographic storage is (generally) a write-once-read-many (WORM) archival storage technique. Where tape and hard drives are magnetic, and optical discs bounce lasers off little pits, holographic storage actually uses a photosensitive medium — like photographic film — to store 3D images that represent data.
Prototypes developed by Lucent and IBM differ slightly, but most holographic data storage systems (HDSS) are based on the same concept. Here are the basic components that are needed to construct an HDSS:
Blue-green argon laser
Beam splitters to split the laser beam
Mirrors to direct the laser beams
LCD panel (spatial light modulator)
Lenses to focus the laser beams
Lithium-niobate crystal or photopolymer
Charge-coupled device (CCD) camera
To record a hologram, a laser beam is split into two beams, each sent along a separate path by mirrors. One beam, the object / signal beam, illuminates the object / scene being recorded. The second beam, the reference beam, is directed at an angle to cross paths and interfere with the light reflected off the object from the object beam. The signal beam is modulated by the data being written, while the reference beam illuminates the target region and effectively keeps track of where the data is being recorded.
Image courtesy Lucent Technologies
When the blue-green argon laser is fired, a beam splitter creates the two beams. The object or signal beam, will go straight, bounce off one mirror and travel through a spatial-light modulator (SLM). An SLM is a liquid crystal display (LCD) that shows pages of raw binary data as clear and dark boxes. The information from the page of binary code is carried by the signal beam around to the light-sensitive lithium-niobate crystal. Some systems use a photopolymer in place of the crystal. The reference beam shoots out the side of the beam splitter and takes a separate path to the crystal. When the two beams meet, the interference pattern that is created stores the data carried by the signal beam in a specific area in the crystal -- the data is stored as a hologram.
If we were to simply illuminate our object with laser light and take a photograph, we would still only be recording the different light intensities of the object; we would not have captured any information about the phase of the light waves after bouncing off the object. That is when the reference beam comes into the scene. The reference source will allow us to record the phase difference of the light wave and thus capture the information which supplies the vital dimensions and depth of the object. Some form of recording medium, such as film, a photo refractive polymer or crystal, a video camera is positioned at the point of interference. The interference pattern is then recorded. As mentioned before, illumination must be accomplished with light of just one wavelength, such as laser, to create a precise interference pattern. To give an illustration, think of pebbles of equal size dropped into a still pond, each sending out concentric waves. Where the waves overlap, there is interference. Some of the waves build on each other constructively; others cancel each other out destructively. This dark light fringe pattern of interference characteristic of the object is recorded.
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. 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.
Holographic memory offers the possibility of storing 1 terabyte (TB) of data in a sugar-cube-sized crystal. A terabyte of data equals 1,000 gigabytes, 1 million megabytes or 1 trillion bytes. Data from more than 1,000 CDs could fit on a holographic memory system. Most computer hard drives only hold 10 to 40 GB of data, a small fraction of what a holographic memory system might hold.
To read data, the reference beam is pointed at exactly the same location, creating a hologram of the data stored by the signal beam. This hologram is immediately "read" by a sensor, much like the CMOS sensor found in a digital camera. Unlike conventional, linear storage mediums (HDD, DVD, tape) every "bit" of the holographic image is read in parallel, potentially resulting in huge data rates.
Image courtesy Lucent Technologies
An advantage of a holographic memory system is that an entire page of data can be retrieved quickly and at one time
During reconstruction, the beam will be diffracted by the crystal to allow the recreation of the original page that was stored. This reconstructed page is then projected onto the charge-coupled device (CCD) camera, which interprets and forwards the digital information to a computer
Basically, depending on the thickness and quality of the storage medium, and the laser, thousands of individual holograms can be stored, stacked on top of each other. Depending on the angle and wavelength of the reference beam, and the position of the media, different holograms can be projected.
By storing and reading out millions of bits at a time, a holographic disc could hold a whole library of films. Movies, video games, and location-based services like interactive maps could be put on postage-stamp-size chips and carried around on cell phones. A person’s entire medical history, including diagnostic images like x-rays, could fit on an ID card and be quickly transmitted to or retrieved from a database.
Holographic storage has some ingenious properties.
A small fragment of a hologram can reconstruct the entire data image. The fragment won’t let you move as far around the image, but for 2D images, like a photograph, it means a scratch isn’t fatal.
Data density is theoretically unlimited. By varying the angle between the reference and illumination beams - or the angle of the media - hundreds of holograms can be stored in the same physical area.
Photographic media has the longest proven lifespan - over a century - of any modern media. Since there’s no physical contact you can read the media millions of times with no degradation.
Applications of Holographic Storage
In general terms, holographic storage is the solution to the storage demands of individuals and organizations.
Holographic storage is for long-term archival storage while it retains the attribute of random access, which also makes it very useful for active working archives.
HVault, a provider of innovative holographic digital data storage solutions, announced a program for early adopters of its holographic storage technology at the Creative Storage Conference 2012.
The HVault Advanced Archive Program is designed to provide a competitive advantage to a select number of organizations that seek to manage big data storage requirements by deploying holographic disks as part of their overall archiving strategy.
Video content owners and cloud storage providers alike have identified big data as a major issue. Although magnetic disk and tape storage solutions become more capable and less costly over time, the requirement to store amounts of data is growing at a faster rate. Holographic storage represents an alternative to traditional hard drive and magnetic tape storage.
HVault’s focus is a holographic disk storage system for archival applications, including both single drive autoloaders and multi-drive libraries. The systems will offer lower cost of ownership than either hard disk or data tape storage. Archival life of the HVault tamper-proof disks exceeds 50 years.
Holographic storage provides a lower total cost of ownership than any other archival storage technology; has a higher media storage density than any other archival solution; lower power consumption, and insensitivity to temperature, humidity, or electromagnetic fields.
According to Coughlin Associates, video distributed over the Internet consumes 60% of digital transmission capacity in North America, and 3D film production and back-catalog demand for archival video is accelerating video storage needs. The size of the video market awaiting digital archiving is currently measured in exabytes, and is exploding.
"The vastly expanding storage needs of the professional video industry have dictated migrating to a secure, long-life format, and holographic storage is the benchmark for archival video storage," said Bland McCartha, vice president of sales for HVault. "The characteristics of our library systems will enable companies who have already digitized their content, as well as the vast collections of analog video that still require digitization, to safely store their content and provide rapid access for monetization of that archival content. There is no other technology that comes close to the benefits of holographic storage for active archive applications."
Holographic storage is much more cost effective than magnetic storage, either disk-based or tape-based. Holographic media has an archival lifetime in excess of 50 years, which eliminates the 2-5 year cycle of replacing magnetic media. Holographic storage systems consume about 1/100th the power of equivalent disk storage and can operate without any special power conditioning or cooling. Holographic media is totally impervious to magnetic fields, static electricity, extremes of temperature and humidity, atmospheric dust or water damage. Holographic media is the only media designed specifically for long-term archiving of digital data.
The future of holographic storage is fraught with unknowns. This technology is very promising. Experts agree that capacity and performance will only increase over time, moving from 300Gbytes to 800Gbytes and finally on to 1.6Tbytes and more over the next 48 months or so. But the pace of improvements will ultimately rest heavily on industry acceptance. Given that holographic technology is currently geared toward a niche in the storage market, it may be years before early product releases give way to more capable and cost-effective systems that appeal to a larger storage audience.
Experts also note the possible introduction of hybrid holographic media. Just as magnetic hard drives are starting to incorporate significant quantities of flash or Ram within the disc, near-term holographic storage media may add some amount of flash memory in the cartridge to provide a degree of re-writability until a suitable rewritable media is developed and productized.
Backward compatibility also remains a significant unknown. No tape drive in any enterprise today is capable of reading a tape written 50 years ago, and the same specter is in the cards for holographic storage. For example, the InPhase product roadmap suggests a third generation of holographic drives in roughly four years and promises backward compatibility with the previous two generations. (Back to first generation in this case.) Well, then what? If the fifth or sixth or 10th generation drives cannot read the holographic discs written today, you'll need to either retain the older drive software and hardware, assuming that it still functions, or rewrite the older discs to the newer media later -- defeating the purpose of such long retention. The same corner case that justifies holographic storage also works against it.
Though it has been, hitherto, an elusory technology consequent upon the other technologies upon which it is dependent, holographic storage is now just a call away. Upon thorough scrutiny and eventual validation of the technology, corporations and individuals who appreciate the viability of this technology, including my humble self, are helping to accentuate this technology.
We can now have unlimited storage space in a very limited space. You can be well assured that you have the value for your money for every holographic storage device you purchase because the whole media, the entire volume of the storage material is utilized as against other storage media where you have only a fraction of the entire media as the actual storage, where most of the remaining parts are mere mechanisms and casing.
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