11-02-2010, 08:32 PM
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ABSTRACT
How do you boost a computer's memory, both in capacity and in speed The usual model for memory storage features a recording/reading device (a "read-write head," a "probe tip," a "stylus,") and a surface on which that device can make its impression. So it's not surprising that some of the most promising research in the memory industry features a simple modification of that paradigm. Instead of just one recording surface, researchers are now thinking of using up to 100 layers, and a corresponding number of recording/reading devices, to store ever-greater quantities of data.
When multiple layers of storage material are coated with fluorescent material, they turn intervening laser beams into fluorescent light. This fluorescent light is immune to corruption from intervening layers and other lasers. More specifically, each base layer is marked with a pattern of "pits." When this layer is coated with fluorescent material, the pits gather a greater thickness of fluorescent stuff. The contrast between pit-thickness and layer-thickness of fluorescent material results in a unique reading of stored data.
1. INTRODUCTION
Requirements for removable media storage devices (RMSDs) used with personal computers have changed significantly since the introduction of the floppy disk in 1971. At one time, desktop computers depended on floppy disks for all of their storage requirements. Even with the advent of multi Gigabyte hard drives and fast Internet connections, floppy disks and other RMSDs are still an integral part of most computer systems, providing:
Transport between computers for data files and software > Backup to preserve data from the hard disks.
A way to load the operating system software in the event of a hard-drive failure.
Some RMSD options available today are approaching the performance, capacity, and cost of hard-disk drives. Considerations for selecting an RMSD include capacity, speed, convenience, durability, data availability, and backward compatibility. Technology options used to read and write data include:
Magnetic formats that use magnetic particles and magnetic fields. > Optical formats that use laser light and optical sensors.
Magneto-optical and magneto-optical hybrids that use a combination of magnetic and optical properties to increase storage capacity.
2. REMOVABLE MEDIA STORAGE DEVICES (RMSDs)
Let us have a glance on the different RMSDs.
2.1 Floppy Disk
Floppy disk drives provide faster data access because they access data randomly. Floppy drives provide an average data access speed of less than 100 milliseconds (ms).
The 1.44-MB, 3.5-inch iloppy is useful for storing and backing up small data files, can be used to boot computer systems, and has been the standard for data interchange between PCs. However it provides only a fraction of the storage capacity required for many files and most software programs in use today. Storing data on floppy drives also i; slow. Data transfer rates average around 0.06 MB/sec.
2.2 Optical Formats
Optical RMSD formats use a laser light source to read and/or write digital data to disc. CD and DVD are two major optical formats. CDs and DVDs have similar compositions consisting of a label, a protective layer, a reflective layer (aluminum, silver, or gold), a digital-data layer molded in polycarbonate, and a thick polycarbonate bottom layer
Label layer
layer
Optical Disk Composition
CD formats include:
¦ Compact disc-read only memory (CD-ROM)
¦ Compact disc-recordable (CD-R)
¦ Compact disc-rewritable (CD-RW)
DVD formats include:
* Digital versatile disc-read only memory (DVD-ROM)
¦ Digital versatile disc-recordable (DVD-R) DVD-RAM (rewritable)
¦ Digital versatile disc-rewritable (DVD-RW)
¦ +RW (rewritable)
2.3 CD-ROM
CD-ROM Standard was established in 1984.They quickly evolved into a low cost digital storage option because of CD-audio industry
Data bits are permanently stored on a CD as a spiral track of physically molded pits in the surface of a plastic data layer that is coated with reflective aluminum. Smooth areas surrounding pits are called lands. CDs are extremely durable because the optical pickup (laser light source, lenses and optical elements, photoelectric sensors, and amplifiers) never touches the disc. Because data is read through the thick bottom layer, most scratches and dust on the disc surface are out of focus, so they do not interfere with the reading process.
One CD-ROM (650-700 MB) storage capacity can store data from more than 450 floppy disks. Data access rate ranges from 80 to 120 ins. Data transfer rates are approximately 6 MB/sec.
2.4 DVD-ROM
The DVD-ROM standard, introduced in 1995 came over as a result of a DVD consortium. Like CD drives, DVD drives read data through the disc substrate reducing interferences from surface dust and scratches. However DVD-ROM technology provides seven times the storage capacity of CDs and accomplishes most of this increase by advancing the technology used for CD systems. The distance between recording tracks is les than half that is used for CDs. The pit size also is less than half that of CDs, which requires a reduced laser wavelength read the smaller sized pits. These features alone give DVD-ROM discs 4.5 times the storage capacity of CDs.
DVD drives can also store on both sides of the disc; manufacturers deliver the two-sided structure by bonding two thinner substrates together, providing the potential to double a DVD's storage capacity. Single sided DVD discs have the two fused substrates, but only one side contains data.
In a DVD, storage of data in the data layers can be:
Single-sided, single layer (4.7 GB)
Double-sided, single layer (9.4 GB)
Single-sided, double layer (8.5 GB)
Double-sided, double layer (17 GB)
Siiigle-sidea. single Inyei (4.TGB) I)oub,e.si(le(l Sinžle (9.4 GB)
T0.6mm I
HI Substrate Q Lacquer
Reflective Layer
Figure: DVD Data Storage Versions
2.5 DVD-R
DVD-R drives were introduced in 1997 to provide write-once capability on DVD-R discs used for producing disc masters in software development and for multimedia post-production. This technology sometimes referred to as DVD-R for authoring, is limited to niche applications because drives and media are expensive.
DVD-R discs employ a photosensitive dye technology similar to CD-R media. At 3.95 GB per side, the first DVD-R discs provided a little less storage capacity than DVD-ROM discs. That capacity has now been extended to the 4.7-GB capacity of DVD-ROM discs. The IX DVD-R data transfer rate is 1.3 MB/sec. Most DVD-ROM drives and DVD video players read DVD-R discs. Slightly modified DVD-R drives and discs have recently become available for general use.
2.6 DVD-RAM
DVD-RAM (rewritable) drives were introduced in 1998. DVD-RAM devices use a phase change technology combined with some embossed land/pit features. Employing a format termed "land groove", data is recorded in the grooves formed on the disc and on the land between the grooves. The initial disc capacity was
2.6 GB per side, but a 4.7 GB- per-side version is now available.
The 4.7-GB DVD-RAM discs come in cartridges that protect the medium from handling damage, such as fingerprints and scratches. A single-sided disc is expected to be removable from the cartridge so it can also be played in DVD-ROM drives that support DVD-RAM. The double-sided disc, providing 4.7GB of storage capacity per side, is not removable from the cartridge.
Each DVD-RAM disc is reported to handle more than 100,000 rewrites. DVD-RAM is specifically designed for PC data storage; DVD-RAM discs use a storage structure based in sectors, instead of the spiral groove structure used for CD data storage. This sector storage is similar to the storage structure used by hard drives. Sector storage results in faster random data access speed.
Because of their high cost relative to CD-RW technology, current consumer-oriented DVD-RAM drives and media are not a popular choice for PC applications. Slow adoption of DVD-RAM reading capability in DVD-ROM drives has also limited DVD-RAM market acceptance.
2.7 DVD-RVV
The DVD-RW drive format is similar to the DVD-R format, but offers rewritability using a phase-change recording layer that is comparable to the phase-change layer used for CD-RW. DVD-RW is intended for consumer video (non -PC) use, but PC applications are also expected for this technology. The first DVD-RW drives based on this format, which also recorded DVD-R discs, were introduced in early 2001.
2.8 +RW
Sony and Philips were founding members of the DVD consortium, but broke away to introduce the DVD+RW (now called +RW) phase change, rewritable technology in 1997. Discs can be written approximately 1000 times, which makes them a good option for video recording, but not optimal for data storage. +RW technology's strongest feature is its backward compatibility with DVD-ROM drives and DVD video players.
2.9 Magneto-Optical Formats
Magneto-optical (MO) technology combines he strengths of magnetic and optical technologies by using a laser to read data and the combination of a laser and magnetic field to write data. The top (label side) of the disk is exposed to a magnetic field to write data, and a laser light source targets the data layer through the bottom substrate to read data.
There are 3.5- and 5.5-inch disk formats that contain a magnetic alloy layer. Magnetic particles in the alloy are very stable and resist changing polarity at room temperature. Data bits re recorded on this magnetic layer by heating it with a focused laser beam in the presence of magnetic field. Changes in the magnetic orientation of the data bits along a track represents Os and Is much like on hard disks and other magnetic media. The magnetic layer also changes the rotation or polarization of reflected laser light depending on the 0 or 1 polarity of the magnetic bits. This property called the "Kerr Effect" and is used to read the data. MO systems also increase the data bits vertically rather than horizontally.
The 3.5-inch disks are available in 128-, 230-, and 640-MB storage capacities. The 5.25-inch disks come in 650-MB and 1.3-, 2.6-, and 5.2-GB sizes. A 9.1 -GB size is expected soon. At less than 25ms, data access times faster than the average 100ms of phase change CD and DVD technologies. MO drives are widely used in Japan for general-purpose storage, similar to the way Zip drives are used in the U.S. Outside of Japan; applications for MO drives typically have been in niche markets for Computer-Aided Design/Computer-Aided Manufacturing (CAD/CAM), document imaging, and high-capacity archives.
2.10 Holographic Data Storage
Researchers promise huge increases in data storage density and data transfer rates with holographic data storage. Unlike methods that store data two-dimensionally on surface layers of media, holographic data is stored volumetrically, or three-dimensionally, throughout the thickness of the media. Additionally, data is stored .and accessed in a page format capable of containing approximately 1 million data bits at a time.
Estimates for this technology predict a storage potential of 200 GB on one 5.25-inch removable disc. This capacity is more than 40 4.7-GB DVD discs. Data transfer rates are estimated at less than 30 MB/sec for a page format containing 1 million data bits. Holographic storage could also be developed in non disc form in any 3D shape.
The majority of holographic data storage research has been funded by the U.S. government through the holographic data storage system and photo refractive information storage consortia. To date, only two companies Lucent Technologies and Imation Corporation, have committed to investing in commercialization of the media. If the technology proves to be commercially feasible, the first systems most likely will be developed for enterprise storage applications. Small robust, holographic storage devices, for use as PC drives, are probably many years from production.
Fluorescent Multi-layer Memory
~~3. FLUORESCENT MULTI-LAYER MEMORY^
Fluorescent multilayer disc (FMD) and fluorescent multilayer card (FMC) are 3D optical storage technologies being developed by C3D, Inc. A disc or card data pit, tilled with a fluorescent material emits fluorescent light when a laser light source is focused on the pit. The emitted light passes through the adjacent data layers unaltered, and is filtered before it reaches the drive's detector, which reduces the effect of stray light and interferences-only data-conveying fluorescent light is detected.
The signal quality of conventional optical reflection system degrades rapidly when additional data layers are added; current research indicates only a few layers are feasible. DVD's two layer data format is an implementation of this research. The filtered, incoherent light of FMD and FMC technology offers the potential for volumetric storage with up to 100 data layers
A FMD requires slightly deeper grooves and data pits, filled with a proprietary fluorescent storage material, for each data layer of a multilayer disc. C3D claims that current CD-ROM/DVD-ROM disc production processes will require relatively minor changes to incorporate fluorescent multilayer technology. High-yield production would be the greatest challenge for this integration process. Initial claims for the ROM version describe a 30-layer disc with a 140-GB storage capacity, equivalent to approximately 20 hours of compressed HDTV data. FMD drives could be made to read existing CD-DVD-ROM discs.
When multiple layers of storage material are coated with fluorescent material, they turn intervening laser beams into fluorescent light. This fluorescent light is immune to corruption from intervening layers and other lasers. More specifically, each base layer is marked with a pattern of "pits." When this layer is coated with fluorescent material, the pits gather a greater thickness of fluorescent stuff. The contrast between pit-thickness and layer-thickness of fluorescent material results in a unique reading of stored data.
This fluorescent material is currently made of polymers that are owned by Constellation 3D. The company intends to market these polymers to other firms, as well as produce the 3D data-storage systems themselves. It looks to be a huge score for the firm. In a field where increasing storage capacities mean greater danger of data corruption, Constellation 3D has found a back door to long-term, high-capacity
Fluorescent Multi-layer Memory
memory. Research has shown that systems using fluorescent material resist corruption much longer than naked systems. And researchers have recently posited devices containing as many as 100 layers separated by fluorescent coatings -- shattering earlier forecasts of feasible storage capacities.
Not only will storage capacities be exponentially increased; the technology is also potentially much faster at accessing information than are single-layer devices. Multiple layers can be read simultaneously, as can different patches of the same layer. This is an important step towards commercializing the product because, up to this point, technologies have tended to focus on either capacity or speed, failing to incorporate both.
Ease of upgrading is another strategic advantage to multilayer fluorescent technology. Existing CD and DVD manufacturing lines can be modified to FMD standards without altering their essential structure. Most systems would only require a few extra steps to deposit coatings with fluorescent materials.
As to the fluorescent material itself, there are a few criteria that need to be met. Most generally, the fluorescent material must be compatible with the layer it's coating, and the wavelength it absorbs must be identical to that used in the drive. It must be a reasonably stable material, although its response time should not be greater than 1 nanosecond. With its refraction index similar to that of its polycarbonate sub layer, the fluorescent material must have high conversion efficiency. Finally, the beam that gets reflected through the fluorescent material should be wavelength-shifted by at least 50nm so that the two beams do not get confused within the system.
3.1 FMD-ROM: operating principle
On the picture you can see how a FMD-ROM looks like.
You can see that a disc is transparent. But where is a reflective layer like on CD and DVD discs The matter is that this technology doesn't need it. Let's consider FM disc in detail.
In optical discs such as CD, DVD and MI the process of reading is implemented the following way. A beam of a semi-conducting laser gets on the surface of an informational layer and then reflects from aluminum (or any other metallic) layer and fixed with a detector-receiver. In FMD there is no reflected laser beam: when a laser beam reaches an informational layer the latter starts radiating.
The principle of operation of FM-discs is based on a phenomenon of photochromism. Some years ago Russian chemists discovered a stable organic
material a "stable photochrome" which when acted upon by a laser beam obtains fluorescent properties.
The matter is that an informational element of FM-disc (photochrome) can change its physical properties (such as color and presence of fluorescence) under influence of a laser of a definite power and wavelength. Initially photochrome doesn't possess fluorescent properties. When switching on a laser a photochemical reaction starts what causes fluorescent properties to appear. When reading, this matter becomes excited again but with a laser of lower power. The fluorescence is caught up by a photo-receiver and is fixed as a value "1".
Besides, according to the company there will be no worsening of the photochrome state with the time.
comparison
REFLECTIVE DISK FLUORESCENT DISK
I Filter
Excited photochrome radiates shifting the spectrum of falling light to the red color side within 30-50 nm what allows differing laser signal from the light from the disc.
Note that this technology allows preventing a problem of multiple inference between layers since the reflected light is not coherent; it passes through layers without any difficulties and is easily defined by a receiver. Let's talk about it a bit in depth.
In usual optical discs (CD/DVD) with increasing number of informational layers a signal gets worse. It's explained by the fact that these technologies use a reflected signal; it means that there is necessity in mirror surfaces. That's why in DVD technology an external layer is made to be semitransparent in order to allow a laser to reach an internal one.
And a signal while passing an external layer leaves a part of its energy because of reflecting. Signals reflected from both layers interfere because of their coherence; it results in losses of useful signal. Increasing number of layers aggravates an effect of multiple interference between the layers what makes reading more complicated. The problem can be solved by improving detector-receivers, but it is possible only in laboratory. In case of fluorescent discs the quality of the signal gets worse much slower with increasing number of layers. According to FMD-ROM developers, even with a hundred layers a useful signal will be acceptable.
3.2 FM-disc
As you can see in the picture a disc consists of several plastic (polycarbonate) layers connected to each other. A layer contains surface structures (pits) which are filled with fluorescent material. When reading a laser focuses on a certain layer and excites its fluorescent elements, and then this radiation is caught by a photo detector.
The developers state that with a blue laser (480 nm) it's possible to increase record density up to tens Terabyte on one FM disc.
Another interesting feature is parallel reading. If we record a sequence of bits not along a track but deep into layers we can increase speed of data access. That's why such disc is called "3-dimensional".
3.3 FM disc production
Many stages of their production are put on the basis of CD and DVD manufacture. However, some alterations are to be made here. In particular, they concern form of surface structures and methods of filling with fluorescent material. Besides, there is no technology of sputtering of aluminum layer what reduces the number of steps.
Mastering process is very similar to that of CD/DVD. A few words on a process of manufacturing CD discs.
As a storage device they use a glass plate covered with a thin photoresistive layer. A laser beam, intensity of which is modulated with digital information, gets into photoresist causing markings that correspond to bits of digital code. After that the photoresist is developed and covered with a metallic layer. This Master-copy after recording contains digital information in the form of pits. Then they make an exact negative copy by a galvanic way which later serves as a press-matrix. This negative can already be used for CD manufacture. But in order to save this single matrix they produce several intermediate copies (negative), and then several press-matrix (the same way) which serve for stamping CDs. After recording of data on an informational surface in vacuum a thin layer of aluminum is sputtered. Outside, the metallic layer is lacquered in order to prevent mechanical damage.
In FMD technology an exact copy of pit is of vital importance since later it's filled with fluorescent material. That's why these two technologies differ. Here, a master-copy is a nickel matrix (a stamp). It is a negative copy, like in CD-technology.
A FM disc consists of several layers that's why the process contains several steps: informational layers are produced separately and then they are combined together.
Technological process of FM discs is divided into two types.
Fluorescent Multi-layer Memory
In the first one there used a method of hot stamping. Each layer is reached by pressing of polycarbonate layer with two stamps (Master-copies) at high temperature. So we receive one layer with two informational sides. Then, pits starts being filled with fluorescent material. And when it becomes hard the informational layers are pressed.
In the picture you can see a structure of a 7-layer disc produced according to the described method.
Seven layer FM disc
The second method uses a process of photopolymerization when a multiple disc is 'reached by stacking of discs one after another which are made from thin informational layers.
Manufacture of one informational layer lies in manufacture of plastic film with definite optical characteristics. The film is 25 to 30 micron in width. The film which will get information soon is either stamped or cut out with a laser. After that the film is installed on an external surface of a nickel matrix that carries a negative copy of produced informational layer. While rotating, photopolymer matter is evenly brought in the space between stamp surface and plastic film. Later, when the photopolymer matter becomes hard the film gets detached from the stamp surface. The base plate now contains pits of definite geometry. A pit's geometry is better in terms of quality than that received when manufacturing matrices for CD or DVD since those technologies use a process of stamping of pits. When a layer with the required position of pits is ready, they are fdled with fluorescent material (it covers evenly the whole informational side). After that the surface is processed chemically in order to reach necessary contrast of pits and flats. Then, in order to check the copy for different defects, photoelements get excited and the whole picture is analyzed with the help of CCD cameras. After that the layers are "stuck" to the base plate 0.6 mm in width. And all this is covered with a protective layer which can be used for graphics decoration. In order to prevent a physical contact with informational layers on the edge of the disc this area is fdled as well with polymeric material, like in CD or DVD technologies.
3.4 FM read devices
The developers say that the drives intended for FM discs will easily understand CD and DVD formats. In structure the drives are similar to CD/DVD ones for example in such parameters as laser, optics, servodrive, tracking and focusing system, different controllers. There appear only systems that can catch and discern fluorescence, and a service in choosing an informational layer.
3.5 Recording on FMD-ROM
It uses a technology WORM (Write Once Read many). For manufacturing FMD WORM (re writable) a different fluorescent material is used. A technology of manufacturing these discs will be the same as for FMD ROM except the fact that they will use another fluorescent material which will be able to change the state under the influence of a laser. And when recording you should follow two rules: ¦ Sufficient power of a laser in order to provide an element with fluorescent
properties.
Threshold power of laser should be used for recording (in order to change fluorescent properties of the material) and for reading must be used less power.
Besides, it's very important to choose a recording method. The FMD developers offer
two record principles.
The first principle (thermal) implies usage of material which possesses
fluorescent properties from the beginning (logical one). And when recording those
segments which are thermally acted upon with a laser lose these properties (logical
zero).
The second principle (chemical) means usage of a material that doesn't possess fluorescent properties form the beginning. When acting upon with a laser a ¦photochemical reaction starts, and the materia! gets fluorescent properties. There, a low-power laser is enough, or even a usual LED. With the latter (LED matrix) there is possible a simultaneous record of the whole array of information.
"Record devices don't differ much from read ones. The only difference lies in a bit different laser form allowing both reading and writing. Besides, we should note that it's possible to combine WORM and ROM on one storage device! For example, imagine a 20-layer disc with 10 layers already recorded and 10 left for a user.
The company C3D has released rewritable FM discs. The record principle is practically the same as in CD-RW technology except for the fact that there it isn't necessary to control reflective ability of a layer - there is enough to convert fluorescent material from one state (absence of fluorescence) into the other (presence of .fluorescence). For example, the whole layer of a FM disc will be covered with a fluorescent material which initially doesn't possess fluorescent properties (logical zero) and when recording a logical one a low-power laser excites a photochemical reaction in the required place. Erasure will be done with the help of a more powerful laser. An advantage of this technology is that the fluorescent material is much more resistant to phase transformations than that used in CD-RW discs that's why you can rewrite it much more times.
4. STATUS OF DEVELOPMENT
Constellation 3D's Fluorescent Multilayer technology enables the production, in a wide variety of form factors, of storage media satisfying these criteria
4.1 Media
The FMD/C media consist of several plastic (polycarbonate) substrates, bonded together. The substrates contain surface structures ("pits") that are filled with a proprietary fluorescent storage material. A major design goal in the development of CD/DVD replacements using this technology was to allow a simple and cost effective upgrade for existing manufacturers of optical devices. FMD technology enables the use, with only relatively minor changes (such as impregnation with fluorescent materials), of existing components and processes from high volume products such as CDs/DVDs, and avoids the need for new infrastructure for media and drive production. The number of process steps per layer is actually reduced, because a reflective metallic layer is not required. For the individual layer of a multilayer disc, metal stampers containing the digital content are produced in a mastering process that is similar to CD or DVD processes. For FMD/C, two replication processes have been developed:
Hot-Embossing:
In this process, thin sheets of polycarbonate are embossed on both sides .with the metal stampers at elevated temperatures. The embossed pits are then filled with the fluorescent dye. After the dye is cured, the individual sheets are bonded together under pressure, resulting in a storage media having multiple layers.
Photo-Polymerization (2P) Process:
In this method, layers are replicated one after the other by forming of "thin replicas". This technology has been demonstrated for up to ten layers.
4.2 Fluorescent Material
Perhaps the most critical component of the storage media is the fluorescent material that converts the incident (incoherent) laser light into incoherent fluorescent light. The materials and associated drives for read-only cards & discs (ROM) are currently the most mature FM technology. Recordable materials and associated drives have also been developed and demonstrated, and improvement of this FM technology continues. FMD/C write/read technology based on proprietary photochromic substances has been demonstrated in Constellation 3D's laboratories during write/ read/erase/re¬-write experiments
4.3 FMD/C ROM (Read Only) Devices
There are several requirements for the fluorescent materials:
1. The fluorescent ROM material has to be compatible with the substrate material
2. The absorption wavelength should be the same wavelength as commercially
available, low cost semiconductor lasers used in CD players
3. The emitted fluorescent light should be wavelength-shifted by at least 50nm, to allow easy separation of the incident and signal light
4. The material should have high conversion efficiency
5. The material should have the refraction index close to the one of the polycarbonate
6. The material should stay stable over a reasonable time
7. Fast response - lnsec
Light-sensitive material:
The photo-polymer composition (PPC) - is a mixture of monomers and oligomers with photoinitiator, which initiates polymerization process under radiation in the certain spectrum range. PPC serves as substrate for the data carrier, oxazine-1, methylene blue, methylene violet and other red dyes serve as the photo-initiator
Pit filling process: .
The working surface of a polycarbonate disc is a plane with pits - cavities 0,5um in size, located in a certain order. Such micro relief can be filled with liquid monomeric or oligomeric substances that turn into hard polymer substances when subjected to UV light. The substances fill the pits and overflow to form a thicker layer on the media surface. The ratio of layer thickness in pit to its thickness on the surface makes the contrast. One of the main tasks of confronting the scientists in developing the process of filling the pits, creating the overflow and choosing the material, was to find the combination of these that provided the largest such contrast.
4.4 FMD/C Recordable (Write Once Read Many) Devices
In addition to the requirements for ROM media, RECORDABLE media require the following:
A writing process where the writing light is able to turn on or off the fluorescence.
A threshold level above which the fluorescent material is changed by the power level of the write, and below which the material is unchanged during any subsequent read-out. Currently 2 techniques have been developed: Thermal Bleaching:
In this technique the material is initially fluorescent. The incident write light heats the material, destroying the fluorescence. The write parameters are similar to CD/R recording and the standard optical writing 15mW laser is well suited for providing CD-R equivalent data writing rates. Materials suitable for applying this technique for use with red, green and blue laser wavelengths have been developed. ¦Photochemical Reaction:
Materials of this class are initially not fluorescent, and the write light initiates photo-chemical reactions, thereby creating fluorescence. The highly non-linear process associated with this reaction causes an effective threshold. Because no heating is involved, the required write power is low, allowing even light emitting diodes (LED arrays) to be used. With LED arrays, pages of information can be written simultaneously, thereby additionally enabling card applications. Current materials are sensitive to green and violet wavelengths.
4.5 FMC "CLEARCARD" Reader
The block diagram above shows the device for reading data from a Fluorescent Multi-Layer Card (FMC)-"ClearCard". A semiconductor laser produces a beam, which is then focused on a selected layer ofthe card. A cylindrical lens forms a 500x2um line, which by means of a scanning mirror scans across a page area of the card. The induced fluorescent light is imaged to a CCD array. A "frame grabber" receives data from the CCD. In the subsequent image processing step the image is aligned, distortions are
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4.6 FMD Disc Drive
The drives have most components in common with CD/DVD systems: Laser, beam-forming optics, spindle, tracking / focusing actuators, control electronics, data channel, data interface. The only additional components are filters to separate the fluorescent light from laser light, and an optical element to correct for different optical path length in the storage medium, depending on the selected layer. Modifications in the electronics include detector circuit with higher sensitivity and the addition of servo electronics to address different layers within the multi-layer disc. A schematic diagram of a FMD drive is shown.
DISK
SPINDLE
LENS SPHERICAL / ABBRECAT10N DICHROMATIC
, CORRECTOR /M„¢-
ACTUATOR. TRACKING FOCUSSING
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FMD DISK DRIVE
5. Industrial Production Prototypes
Constellation 3D, Inc. has developed and proven the basic technology and will continue to develop fully functional prototypes of end-user products. With respect to each of the following products, the company will seek and establish joint ventures with strategic partners having an established market share and manufacturing capability in the relevant product market.
5.1 FMC ClearCard ROM
The planned initial production model is a credit card-sized ClearCard -ROM with up to 20 layers, 400 MB/cm2 data density and up to 10GB capacity* - twice current single-sided DVD disc, but at a fraction of the cost and size. The design of the reader will be simple, with virtually no moving parts, making them resilient to all kinds of shocks. The potential number of applications for which these cards could be used are almost limitless - from e-books and home entertainment systems to e-books and archival and navigational systems. The ClearCard could also be used in many applications where a CD/DVD discs are currently used. The cost of production of these cards is less than $10.
Constellation 3D has recently confirmed in its labs the feasibility of production of a 50.-layer.ClearCard ROM with a storage capacity of 1 Terabyte and data transfer speeds of up to 1 Gigabit/second. The card would be intended for use in HDTV, Video & Music-on-demand and other multimedia applications.
5.2 FMC ClearCard RECORDABLE
The card is a compact version of the FMC ClearCard that enables the user to record the initial information to be stored. The planned initial production model is a credit card sized 10-layer disk with a 1 Gigabyte capacity. It is designed to fit into devices such as laptop and hand-held computers, digital cameras, cellular phones and video recorders and players, for which it will offer light weight, high capacity storage and quick access to data. Next generations of recordable cards will have nearly as much capacity read only cards. For cameras and video players, the ClearCard-RECORDABLE will not only offer the same gains as for laptop and hand-held computers but also offer higher quality video. This technology will be ideal for downloading information from the Internet.
portable
5.3 FMD ROM
This disc takes the CD-ROM & DVD-ROM concept to the next level. The planned initial production model is a 120mm 10-layer disk with 140 Gigabyte capacity - vs. less than 18 Gigabytes for a maximum capacity DVD - giving it the capacity to store up to 20 hours of compressed HDTV film viewing. As mentioned above, existing CD & DVD 120mm disc and drive manufacturing equipment will be adaptable with minimal re-tooling to accommodate the new technology. The new FMD drives will also be backward compatible with (i.e., capable of reading) existing CD & DVD media.
However, it is anticipated that the majority of users will at an early stage decide to take advantage of the much larger capacities and superior performance characteristics of the new FMD discs and make it their media of choice for future data storage applications.
5.4 FMD/C Re-Writable
Re-Writable optical memory carriers have been recently been gaining attention within the optical memory community and provides the maximum amount of flexibility in the determination of data stored at any given time - it is a fundamental requirement of hard disk drives in PCs. In between the two extreme approaches to storing memory, ROM and Re-Writable, are data storage applications where the user requires the flexibility of deciding the initial data to be stored on the media and then the certainty that the data will not later be erased or amended. The initial solution to the most effective data management is FMD/C RECORDABLE storage carriers of very significant capacity. In particular Constellation 3D intends to produce a credit card sized ClearCard -RECORDABLE with 4.7 GBytes capacity and costing under $10, thereby providing users of hand held devices with a cost effective solution to their Internet downloading and other data write-once needs. The next generation products will include genuinely re-writable layers based on most recent development carried out by Constellation 3D.
5.5 Media Manufacturing Technology
Fluorescent media manufacturing process described here utilizes many processes that are typical for CD and/or DVD manufacturing. However, fluorescent media requires many proprietary polymers and compositions that were exclusively developed by Constellation 3D Inc. Company intends to make these materials available to media manufacturers through its selected industry affdiated partners. Media manufacturing process described in this document relies on well known optical disc replication process. Further developments related to increase of data storage capacity to the level of multi-hundreds of gigabytes per disc, will require adoption of other disc manufacturing technologies currently under internal development:
¢ Pre-mastering and mastering process Pre-mastering and mastering processes are very similar to those utilized by CD/DVD industry. However, certain modifications of mastering process will be required (namely glass master and stamper preparation). These modifications are mainly related to pit geometries that are designed to facilitate reliable pit replication and pit filling
¢ Replica manufacturing
Replica manufacturing involves preparation of circular substrates made of low birefringence plastic film (polycarbonate, PMMA or other films with appropriate optical characteristics). Film thickness is between 25 to 30 microns. Prior to usage, substrates are die or laser cut to appropriate diameter (media dependent, see above). Prepared substrate is placed over radial bead of photo-polymer deposited onto nickel matrix top surface (stamper). During spinning process photo-polymer evenly spreads between stamper surface and plastic substrate. Subsequently, UV curing hardens photo¬polymer and now substrate can be separated from top surface of stamper. Substrate contains precise pit geometry. Precision of pit replication exceeds quality of injection-molded substrates (such as CDs or DVDs).
¢ Pit filling
During pit filling, fluorescent dye-polymer evenly spreads over entire replica's informational side by utilizing of spin-coating process (similarly to CD-R dye application). After dye-polymer is UV cured, certain chemical bleaching process is applied to achieve the desired signal contrast ratio of pits and lands
¢ Replica inspection
Each replica is optically inspected to verify proper dye-polymer filling of pits. Such inspection is achieved by observing of emitted light from entire area of data pits by utilizing of CCD camera. At this stage replica is optically inspected for various physical defects such scratches, inclusions and alike
¢ Layer bonding
Layers or replicas are centrally bonded onto optical spacer (0.6 mm thick polycarbonate or PMMA substrate), by utilizing capillary bonding method well known to DVD industry. Since replicas are thin and thus more pliable, formation of air bubbles in the bonding layer is minimized. Requirements to centricity of informational layers are similar to DVD discs (or +/- 25 micron).
¢ Disc decoration
After multiple replicas are bonded on the top of optical spacer (see above), additional Support/protection substrate is bonded on the stack top. These decorated elsewhere substrates are made of solid color inexpensive plastic materials
Fluorescent Multi-layer Memory ¢ Edge sealing
In order to prevent layer separation by physical contact, disc otiter edge is sealed with UV curable photo-polymers typically used for protection of CDs and DVDs.
5.6 FMD/C Advantages
The main advantages of multilayer fluorescent read out are:
1. The multi-layer system is optically transparent and homogeneous.
2. Low absorption in each layer.
3. No absorption for the emitted signal fluorescent light.
4. Lower than CD/DVD sensitivity to imperfections in media and drives. The
fluorescent technique does not depend on interference effects and requires less stringent
manufacturing tolerances for media and drives.
5. The emitted fluorescent light from any given layer is non-coherent, eliminating the problem of parasite interference.
6. The limited lateral spatial resolution for this system is twice that for coherent light based systems (e.g. current CD/DVD reflective systems). In the case of FMD/C, this two-fold improvement over three (3) dimensions, results in an eight-fold improvement in achievable data density.
7. FMD technology is compatible with current CD and DVD formats, having the capacity to handle the same data rates over each of its layers.
The above qualities make FMC unique in its technological capability to facilitate production of a multilayer optical card†ClearCard, in any form factor including postage stamp sized SmartMedia, credit card sized ClearCard, or otherwise. The capacity and speed of reading from these cards can be enormous. For instance, with the level of existing technology ClearCard of 16 cm2 of area with 50 layers can furnish consumers with 1 terabyte capacity and, through parallel access to all its layers, allow over 1 gigabit/sec speed of reading. Another major advantage, for both cards and discs using the technology, is the ability to read data on every layer of the media in parallel, thereby allowing the potential of much grater data transfer rates compared with single layer media. This can be combined with parallel reading from multiple sectors of the same layer to increase data speeds still further, producing 3-dimensional data transfer.
Here is a table demonstrating one of the projects of C3D:50 GB disc (12 layers):
Parameter CD DVD FMD
Disc diameter, mm 120 120 130
Capacity, GBytes -,.64 17,4 50,8
Number of layers i i 2 12
Distance between layers, micron - 40 25±5
Total width of layers, micron 0,11 2 275
Optical system wavelength, nm 780 635-650 532
Distance between tracks, micron 1,6 0,74 0,8
6ž Conclusion
Constellation 3D's fluorescent multilayer optical data storage technology can be utilized to produce compact, removable, inexpensive, rugged, ultra-high capacity data storage devices, having data transfer speeds in excess of lGbit/sec. The company wishes to maintain its focus on research and development in the field of fluorescent multilayer optical storage, with the intention of continually expanding the limits and capabilities of this technology. Having successfully demonstrated prototype multilayer cards and discs incorporating FMC/D technology, the way is now open - through joint ventures with industry leaders to commence industrial production of these devices and take them into the mainstream.
7, FUTURE SCOPE
Dell monitoring advancements in optical technology and expects the cost and performance of CD-RW drives become more competitive with the magnetic formats. Dell plan to offer CD-RW/DVD ROM Combo Drives when reasonably priced. Reliable devices become available. These devices should eventually replace current CD-RW drive and offer convenience, large storage capacity that are backward compatible with previous CD formats, and DVD ROM readability. Dell expects DVD-RAM systems to be adopted by high end users initially. Ram bo systems when available are expected to provide another system in a evolution to a universal RMSD providing a larger capacity drive capable of reading and writing to the most popular CD, DVD format.
Dell is monitoring the development of Blue laser and FMD/FMC technologies for their potential application with existing optical formats. The smaller wavelength of the blue laser may allow data density increase from 3 to 4 times the storage capacity of current optical storage device and a new smaller card format could provide an attractive, high capacity alternative to disk storage. By adding an extra layer and advantages of blue laser second and third generation of disk will be produced of capacity 1000GB.
Bibliography
[l].Ingolf Sander " White Paper on Fluorescent Multilayer Optical Data Storage ",
Constellation 3D, NY, USA [2]. http://vvww.us.net [3]. http://pcstats.com [4]. http://digit-life.com [5].http://dell.com [6]. http://computer.org
CONTENTS
Page
1. INTRODUCTION 01
2. REMOVABLE MEDIA STORAGE DEVICES 02
2.1 Floppy Disk 02
2.2 Optical Formats 02
2.3 CD-ROM 03
2.4 DVD-ROM 03
2.5 DVD-R 04
2.6 DVD-RAM 05
2.7 DVD-RW 05
2.8 +RW 06
2.9 Magneto-Optical Formats 06
2.10 Holographic Data Storage 07
3. FLUORESCENT MULTI-LAYER MEMORY 08
3.1 FMD-ROM: operating principle 10
3.2 FM-disc 12
3.3 FM disc production 13 3.4.FM read devices 15
3.5 Recording on FMD-ROM 15
4. STATUS OF DEVELOPMENT 17
4.1 Media 17
4.2 Fluorescent Material 17
4.3 FMD/C ROM (Read Only) Devices 18
4.4 FMD/C Recordable (Write Once Read Many) Devices 19 . 4.5 FMC "CLEARCARD" READER 19
4.6 FMD DISC DRIVE 20
5. INDUSTRIAL PRODUCTION PROTOTYPES 22
5.1 EMC ClearCard ROM 22
5.2 FMC ClearCard RECORDABLE 22
5.3 FMD ROM 23
5.4 FMD/C Re-Writable 24
5.5 Media Manufacturing Technology 24
5.6 FMD/C Advantages 26
6. CONCLUSION 28
7. FUTURE SCOPE 29
8. BIBLIOGRAPHY 30
ABSTRACT
How do you boost a computer's memory, both in capacity and in speed The usual model for memory storage features a recording/reading device (a "read-write head," a "probe tip," a "stylus,") and a surface on which that device can make its impression. So it's not surprising that some of the most promising research in the memory industry features a simple modification of that paradigm. Instead of just one recording surface, researchers are now thinking of using up to 100 layers, and a corresponding number of recording/reading devices, to store ever-greater quantities of data.
When multiple layers of storage material are coated with fluorescent material, they turn intervening laser beams into fluorescent light. This fluorescent light is immune to corruption from intervening layers and other lasers. More specifically, each base layer is marked with a pattern of "pits." When this layer is coated with fluorescent material, the pits gather a greater thickness of fluorescent stuff. The contrast between pit-thickness and layer-thickness of fluorescent material results in a unique reading of stored data.
1. INTRODUCTION
Requirements for removable media storage devices (RMSDs) used with personal computers have changed significantly since the introduction of the floppy disk in 1971. At one time, desktop computers depended on floppy disks for all of their storage requirements. Even with the advent of multi Gigabyte hard drives and fast Internet connections, floppy disks and other RMSDs are still an integral part of most computer systems, providing:
Transport between computers for data files and software > Backup to preserve data from the hard disks.
A way to load the operating system software in the event of a hard-drive failure.
Some RMSD options available today are approaching the performance, capacity, and cost of hard-disk drives. Considerations for selecting an RMSD include capacity, speed, convenience, durability, data availability, and backward compatibility. Technology options used to read and write data include:
Magnetic formats that use magnetic particles and magnetic fields. > Optical formats that use laser light and optical sensors.
Magneto-optical and magneto-optical hybrids that use a combination of magnetic and optical properties to increase storage capacity.
2. REMOVABLE MEDIA STORAGE DEVICES (RMSDs)
Let us have a glance on the different RMSDs.
2.1 Floppy Disk
Floppy disk drives provide faster data access because they access data randomly. Floppy drives provide an average data access speed of less than 100 milliseconds (ms).
The 1.44-MB, 3.5-inch iloppy is useful for storing and backing up small data files, can be used to boot computer systems, and has been the standard for data interchange between PCs. However it provides only a fraction of the storage capacity required for many files and most software programs in use today. Storing data on floppy drives also i; slow. Data transfer rates average around 0.06 MB/sec.
2.2 Optical Formats
Optical RMSD formats use a laser light source to read and/or write digital data to disc. CD and DVD are two major optical formats. CDs and DVDs have similar compositions consisting of a label, a protective layer, a reflective layer (aluminum, silver, or gold), a digital-data layer molded in polycarbonate, and a thick polycarbonate bottom layer
Label layer
layer
Optical Disk Composition
CD formats include:
¦ Compact disc-read only memory (CD-ROM)
¦ Compact disc-recordable (CD-R)
¦ Compact disc-rewritable (CD-RW)
DVD formats include:
* Digital versatile disc-read only memory (DVD-ROM)
¦ Digital versatile disc-recordable (DVD-R) DVD-RAM (rewritable)
¦ Digital versatile disc-rewritable (DVD-RW)
¦ +RW (rewritable)
2.3 CD-ROM
CD-ROM Standard was established in 1984.They quickly evolved into a low cost digital storage option because of CD-audio industry
Data bits are permanently stored on a CD as a spiral track of physically molded pits in the surface of a plastic data layer that is coated with reflective aluminum. Smooth areas surrounding pits are called lands. CDs are extremely durable because the optical pickup (laser light source, lenses and optical elements, photoelectric sensors, and amplifiers) never touches the disc. Because data is read through the thick bottom layer, most scratches and dust on the disc surface are out of focus, so they do not interfere with the reading process.
One CD-ROM (650-700 MB) storage capacity can store data from more than 450 floppy disks. Data access rate ranges from 80 to 120 ins. Data transfer rates are approximately 6 MB/sec.
2.4 DVD-ROM
The DVD-ROM standard, introduced in 1995 came over as a result of a DVD consortium. Like CD drives, DVD drives read data through the disc substrate reducing interferences from surface dust and scratches. However DVD-ROM technology provides seven times the storage capacity of CDs and accomplishes most of this increase by advancing the technology used for CD systems. The distance between recording tracks is les than half that is used for CDs. The pit size also is less than half that of CDs, which requires a reduced laser wavelength read the smaller sized pits. These features alone give DVD-ROM discs 4.5 times the storage capacity of CDs.
DVD drives can also store on both sides of the disc; manufacturers deliver the two-sided structure by bonding two thinner substrates together, providing the potential to double a DVD's storage capacity. Single sided DVD discs have the two fused substrates, but only one side contains data.
In a DVD, storage of data in the data layers can be:
Single-sided, single layer (4.7 GB)
Double-sided, single layer (9.4 GB)
Single-sided, double layer (8.5 GB)
Double-sided, double layer (17 GB)
Siiigle-sidea. single Inyei (4.TGB) I)oub,e.si(le(l Sinžle (9.4 GB)
T0.6mm I
HI Substrate Q Lacquer
Reflective Layer
Figure: DVD Data Storage Versions
2.5 DVD-R
DVD-R drives were introduced in 1997 to provide write-once capability on DVD-R discs used for producing disc masters in software development and for multimedia post-production. This technology sometimes referred to as DVD-R for authoring, is limited to niche applications because drives and media are expensive.
DVD-R discs employ a photosensitive dye technology similar to CD-R media. At 3.95 GB per side, the first DVD-R discs provided a little less storage capacity than DVD-ROM discs. That capacity has now been extended to the 4.7-GB capacity of DVD-ROM discs. The IX DVD-R data transfer rate is 1.3 MB/sec. Most DVD-ROM drives and DVD video players read DVD-R discs. Slightly modified DVD-R drives and discs have recently become available for general use.
2.6 DVD-RAM
DVD-RAM (rewritable) drives were introduced in 1998. DVD-RAM devices use a phase change technology combined with some embossed land/pit features. Employing a format termed "land groove", data is recorded in the grooves formed on the disc and on the land between the grooves. The initial disc capacity was
2.6 GB per side, but a 4.7 GB- per-side version is now available.
The 4.7-GB DVD-RAM discs come in cartridges that protect the medium from handling damage, such as fingerprints and scratches. A single-sided disc is expected to be removable from the cartridge so it can also be played in DVD-ROM drives that support DVD-RAM. The double-sided disc, providing 4.7GB of storage capacity per side, is not removable from the cartridge.
Each DVD-RAM disc is reported to handle more than 100,000 rewrites. DVD-RAM is specifically designed for PC data storage; DVD-RAM discs use a storage structure based in sectors, instead of the spiral groove structure used for CD data storage. This sector storage is similar to the storage structure used by hard drives. Sector storage results in faster random data access speed.
Because of their high cost relative to CD-RW technology, current consumer-oriented DVD-RAM drives and media are not a popular choice for PC applications. Slow adoption of DVD-RAM reading capability in DVD-ROM drives has also limited DVD-RAM market acceptance.
2.7 DVD-RVV
The DVD-RW drive format is similar to the DVD-R format, but offers rewritability using a phase-change recording layer that is comparable to the phase-change layer used for CD-RW. DVD-RW is intended for consumer video (non -PC) use, but PC applications are also expected for this technology. The first DVD-RW drives based on this format, which also recorded DVD-R discs, were introduced in early 2001.
2.8 +RW
Sony and Philips were founding members of the DVD consortium, but broke away to introduce the DVD+RW (now called +RW) phase change, rewritable technology in 1997. Discs can be written approximately 1000 times, which makes them a good option for video recording, but not optimal for data storage. +RW technology's strongest feature is its backward compatibility with DVD-ROM drives and DVD video players.
2.9 Magneto-Optical Formats
Magneto-optical (MO) technology combines he strengths of magnetic and optical technologies by using a laser to read data and the combination of a laser and magnetic field to write data. The top (label side) of the disk is exposed to a magnetic field to write data, and a laser light source targets the data layer through the bottom substrate to read data.
There are 3.5- and 5.5-inch disk formats that contain a magnetic alloy layer. Magnetic particles in the alloy are very stable and resist changing polarity at room temperature. Data bits re recorded on this magnetic layer by heating it with a focused laser beam in the presence of magnetic field. Changes in the magnetic orientation of the data bits along a track represents Os and Is much like on hard disks and other magnetic media. The magnetic layer also changes the rotation or polarization of reflected laser light depending on the 0 or 1 polarity of the magnetic bits. This property called the "Kerr Effect" and is used to read the data. MO systems also increase the data bits vertically rather than horizontally.
The 3.5-inch disks are available in 128-, 230-, and 640-MB storage capacities. The 5.25-inch disks come in 650-MB and 1.3-, 2.6-, and 5.2-GB sizes. A 9.1 -GB size is expected soon. At less than 25ms, data access times faster than the average 100ms of phase change CD and DVD technologies. MO drives are widely used in Japan for general-purpose storage, similar to the way Zip drives are used in the U.S. Outside of Japan; applications for MO drives typically have been in niche markets for Computer-Aided Design/Computer-Aided Manufacturing (CAD/CAM), document imaging, and high-capacity archives.
2.10 Holographic Data Storage
Researchers promise huge increases in data storage density and data transfer rates with holographic data storage. Unlike methods that store data two-dimensionally on surface layers of media, holographic data is stored volumetrically, or three-dimensionally, throughout the thickness of the media. Additionally, data is stored .and accessed in a page format capable of containing approximately 1 million data bits at a time.
Estimates for this technology predict a storage potential of 200 GB on one 5.25-inch removable disc. This capacity is more than 40 4.7-GB DVD discs. Data transfer rates are estimated at less than 30 MB/sec for a page format containing 1 million data bits. Holographic storage could also be developed in non disc form in any 3D shape.
The majority of holographic data storage research has been funded by the U.S. government through the holographic data storage system and photo refractive information storage consortia. To date, only two companies Lucent Technologies and Imation Corporation, have committed to investing in commercialization of the media. If the technology proves to be commercially feasible, the first systems most likely will be developed for enterprise storage applications. Small robust, holographic storage devices, for use as PC drives, are probably many years from production.
Fluorescent Multi-layer Memory
~~3. FLUORESCENT MULTI-LAYER MEMORY^
Fluorescent multilayer disc (FMD) and fluorescent multilayer card (FMC) are 3D optical storage technologies being developed by C3D, Inc. A disc or card data pit, tilled with a fluorescent material emits fluorescent light when a laser light source is focused on the pit. The emitted light passes through the adjacent data layers unaltered, and is filtered before it reaches the drive's detector, which reduces the effect of stray light and interferences-only data-conveying fluorescent light is detected.
The signal quality of conventional optical reflection system degrades rapidly when additional data layers are added; current research indicates only a few layers are feasible. DVD's two layer data format is an implementation of this research. The filtered, incoherent light of FMD and FMC technology offers the potential for volumetric storage with up to 100 data layers
A FMD requires slightly deeper grooves and data pits, filled with a proprietary fluorescent storage material, for each data layer of a multilayer disc. C3D claims that current CD-ROM/DVD-ROM disc production processes will require relatively minor changes to incorporate fluorescent multilayer technology. High-yield production would be the greatest challenge for this integration process. Initial claims for the ROM version describe a 30-layer disc with a 140-GB storage capacity, equivalent to approximately 20 hours of compressed HDTV data. FMD drives could be made to read existing CD-DVD-ROM discs.
When multiple layers of storage material are coated with fluorescent material, they turn intervening laser beams into fluorescent light. This fluorescent light is immune to corruption from intervening layers and other lasers. More specifically, each base layer is marked with a pattern of "pits." When this layer is coated with fluorescent material, the pits gather a greater thickness of fluorescent stuff. The contrast between pit-thickness and layer-thickness of fluorescent material results in a unique reading of stored data.
This fluorescent material is currently made of polymers that are owned by Constellation 3D. The company intends to market these polymers to other firms, as well as produce the 3D data-storage systems themselves. It looks to be a huge score for the firm. In a field where increasing storage capacities mean greater danger of data corruption, Constellation 3D has found a back door to long-term, high-capacity
Fluorescent Multi-layer Memory
memory. Research has shown that systems using fluorescent material resist corruption much longer than naked systems. And researchers have recently posited devices containing as many as 100 layers separated by fluorescent coatings -- shattering earlier forecasts of feasible storage capacities.
Not only will storage capacities be exponentially increased; the technology is also potentially much faster at accessing information than are single-layer devices. Multiple layers can be read simultaneously, as can different patches of the same layer. This is an important step towards commercializing the product because, up to this point, technologies have tended to focus on either capacity or speed, failing to incorporate both.
Ease of upgrading is another strategic advantage to multilayer fluorescent technology. Existing CD and DVD manufacturing lines can be modified to FMD standards without altering their essential structure. Most systems would only require a few extra steps to deposit coatings with fluorescent materials.
As to the fluorescent material itself, there are a few criteria that need to be met. Most generally, the fluorescent material must be compatible with the layer it's coating, and the wavelength it absorbs must be identical to that used in the drive. It must be a reasonably stable material, although its response time should not be greater than 1 nanosecond. With its refraction index similar to that of its polycarbonate sub layer, the fluorescent material must have high conversion efficiency. Finally, the beam that gets reflected through the fluorescent material should be wavelength-shifted by at least 50nm so that the two beams do not get confused within the system.
3.1 FMD-ROM: operating principle
On the picture you can see how a FMD-ROM looks like.
You can see that a disc is transparent. But where is a reflective layer like on CD and DVD discs The matter is that this technology doesn't need it. Let's consider FM disc in detail.
In optical discs such as CD, DVD and MI the process of reading is implemented the following way. A beam of a semi-conducting laser gets on the surface of an informational layer and then reflects from aluminum (or any other metallic) layer and fixed with a detector-receiver. In FMD there is no reflected laser beam: when a laser beam reaches an informational layer the latter starts radiating.
The principle of operation of FM-discs is based on a phenomenon of photochromism. Some years ago Russian chemists discovered a stable organic
material a "stable photochrome" which when acted upon by a laser beam obtains fluorescent properties.
The matter is that an informational element of FM-disc (photochrome) can change its physical properties (such as color and presence of fluorescence) under influence of a laser of a definite power and wavelength. Initially photochrome doesn't possess fluorescent properties. When switching on a laser a photochemical reaction starts what causes fluorescent properties to appear. When reading, this matter becomes excited again but with a laser of lower power. The fluorescence is caught up by a photo-receiver and is fixed as a value "1".
Besides, according to the company there will be no worsening of the photochrome state with the time.
comparison
REFLECTIVE DISK FLUORESCENT DISK
I Filter
Excited photochrome radiates shifting the spectrum of falling light to the red color side within 30-50 nm what allows differing laser signal from the light from the disc.
Note that this technology allows preventing a problem of multiple inference between layers since the reflected light is not coherent; it passes through layers without any difficulties and is easily defined by a receiver. Let's talk about it a bit in depth.
In usual optical discs (CD/DVD) with increasing number of informational layers a signal gets worse. It's explained by the fact that these technologies use a reflected signal; it means that there is necessity in mirror surfaces. That's why in DVD technology an external layer is made to be semitransparent in order to allow a laser to reach an internal one.
And a signal while passing an external layer leaves a part of its energy because of reflecting. Signals reflected from both layers interfere because of their coherence; it results in losses of useful signal. Increasing number of layers aggravates an effect of multiple interference between the layers what makes reading more complicated. The problem can be solved by improving detector-receivers, but it is possible only in laboratory. In case of fluorescent discs the quality of the signal gets worse much slower with increasing number of layers. According to FMD-ROM developers, even with a hundred layers a useful signal will be acceptable.
3.2 FM-disc
As you can see in the picture a disc consists of several plastic (polycarbonate) layers connected to each other. A layer contains surface structures (pits) which are filled with fluorescent material. When reading a laser focuses on a certain layer and excites its fluorescent elements, and then this radiation is caught by a photo detector.
The developers state that with a blue laser (480 nm) it's possible to increase record density up to tens Terabyte on one FM disc.
Another interesting feature is parallel reading. If we record a sequence of bits not along a track but deep into layers we can increase speed of data access. That's why such disc is called "3-dimensional".
3.3 FM disc production
Many stages of their production are put on the basis of CD and DVD manufacture. However, some alterations are to be made here. In particular, they concern form of surface structures and methods of filling with fluorescent material. Besides, there is no technology of sputtering of aluminum layer what reduces the number of steps.
Mastering process is very similar to that of CD/DVD. A few words on a process of manufacturing CD discs.
As a storage device they use a glass plate covered with a thin photoresistive layer. A laser beam, intensity of which is modulated with digital information, gets into photoresist causing markings that correspond to bits of digital code. After that the photoresist is developed and covered with a metallic layer. This Master-copy after recording contains digital information in the form of pits. Then they make an exact negative copy by a galvanic way which later serves as a press-matrix. This negative can already be used for CD manufacture. But in order to save this single matrix they produce several intermediate copies (negative), and then several press-matrix (the same way) which serve for stamping CDs. After recording of data on an informational surface in vacuum a thin layer of aluminum is sputtered. Outside, the metallic layer is lacquered in order to prevent mechanical damage.
In FMD technology an exact copy of pit is of vital importance since later it's filled with fluorescent material. That's why these two technologies differ. Here, a master-copy is a nickel matrix (a stamp). It is a negative copy, like in CD-technology.
A FM disc consists of several layers that's why the process contains several steps: informational layers are produced separately and then they are combined together.
Technological process of FM discs is divided into two types.
Fluorescent Multi-layer Memory
In the first one there used a method of hot stamping. Each layer is reached by pressing of polycarbonate layer with two stamps (Master-copies) at high temperature. So we receive one layer with two informational sides. Then, pits starts being filled with fluorescent material. And when it becomes hard the informational layers are pressed.
In the picture you can see a structure of a 7-layer disc produced according to the described method.
Seven layer FM disc
The second method uses a process of photopolymerization when a multiple disc is 'reached by stacking of discs one after another which are made from thin informational layers.
Manufacture of one informational layer lies in manufacture of plastic film with definite optical characteristics. The film is 25 to 30 micron in width. The film which will get information soon is either stamped or cut out with a laser. After that the film is installed on an external surface of a nickel matrix that carries a negative copy of produced informational layer. While rotating, photopolymer matter is evenly brought in the space between stamp surface and plastic film. Later, when the photopolymer matter becomes hard the film gets detached from the stamp surface. The base plate now contains pits of definite geometry. A pit's geometry is better in terms of quality than that received when manufacturing matrices for CD or DVD since those technologies use a process of stamping of pits. When a layer with the required position of pits is ready, they are fdled with fluorescent material (it covers evenly the whole informational side). After that the surface is processed chemically in order to reach necessary contrast of pits and flats. Then, in order to check the copy for different defects, photoelements get excited and the whole picture is analyzed with the help of CCD cameras. After that the layers are "stuck" to the base plate 0.6 mm in width. And all this is covered with a protective layer which can be used for graphics decoration. In order to prevent a physical contact with informational layers on the edge of the disc this area is fdled as well with polymeric material, like in CD or DVD technologies.
3.4 FM read devices
The developers say that the drives intended for FM discs will easily understand CD and DVD formats. In structure the drives are similar to CD/DVD ones for example in such parameters as laser, optics, servodrive, tracking and focusing system, different controllers. There appear only systems that can catch and discern fluorescence, and a service in choosing an informational layer.
3.5 Recording on FMD-ROM
It uses a technology WORM (Write Once Read many). For manufacturing FMD WORM (re writable) a different fluorescent material is used. A technology of manufacturing these discs will be the same as for FMD ROM except the fact that they will use another fluorescent material which will be able to change the state under the influence of a laser. And when recording you should follow two rules: ¦ Sufficient power of a laser in order to provide an element with fluorescent
properties.
Threshold power of laser should be used for recording (in order to change fluorescent properties of the material) and for reading must be used less power.
Besides, it's very important to choose a recording method. The FMD developers offer
two record principles.
The first principle (thermal) implies usage of material which possesses
fluorescent properties from the beginning (logical one). And when recording those
segments which are thermally acted upon with a laser lose these properties (logical
zero).
The second principle (chemical) means usage of a material that doesn't possess fluorescent properties form the beginning. When acting upon with a laser a ¦photochemical reaction starts, and the materia! gets fluorescent properties. There, a low-power laser is enough, or even a usual LED. With the latter (LED matrix) there is possible a simultaneous record of the whole array of information.
"Record devices don't differ much from read ones. The only difference lies in a bit different laser form allowing both reading and writing. Besides, we should note that it's possible to combine WORM and ROM on one storage device! For example, imagine a 20-layer disc with 10 layers already recorded and 10 left for a user.
The company C3D has released rewritable FM discs. The record principle is practically the same as in CD-RW technology except for the fact that there it isn't necessary to control reflective ability of a layer - there is enough to convert fluorescent material from one state (absence of fluorescence) into the other (presence of .fluorescence). For example, the whole layer of a FM disc will be covered with a fluorescent material which initially doesn't possess fluorescent properties (logical zero) and when recording a logical one a low-power laser excites a photochemical reaction in the required place. Erasure will be done with the help of a more powerful laser. An advantage of this technology is that the fluorescent material is much more resistant to phase transformations than that used in CD-RW discs that's why you can rewrite it much more times.
4. STATUS OF DEVELOPMENT
Constellation 3D's Fluorescent Multilayer technology enables the production, in a wide variety of form factors, of storage media satisfying these criteria
4.1 Media
The FMD/C media consist of several plastic (polycarbonate) substrates, bonded together. The substrates contain surface structures ("pits") that are filled with a proprietary fluorescent storage material. A major design goal in the development of CD/DVD replacements using this technology was to allow a simple and cost effective upgrade for existing manufacturers of optical devices. FMD technology enables the use, with only relatively minor changes (such as impregnation with fluorescent materials), of existing components and processes from high volume products such as CDs/DVDs, and avoids the need for new infrastructure for media and drive production. The number of process steps per layer is actually reduced, because a reflective metallic layer is not required. For the individual layer of a multilayer disc, metal stampers containing the digital content are produced in a mastering process that is similar to CD or DVD processes. For FMD/C, two replication processes have been developed:
Hot-Embossing:
In this process, thin sheets of polycarbonate are embossed on both sides .with the metal stampers at elevated temperatures. The embossed pits are then filled with the fluorescent dye. After the dye is cured, the individual sheets are bonded together under pressure, resulting in a storage media having multiple layers.
Photo-Polymerization (2P) Process:
In this method, layers are replicated one after the other by forming of "thin replicas". This technology has been demonstrated for up to ten layers.
4.2 Fluorescent Material
Perhaps the most critical component of the storage media is the fluorescent material that converts the incident (incoherent) laser light into incoherent fluorescent light. The materials and associated drives for read-only cards & discs (ROM) are currently the most mature FM technology. Recordable materials and associated drives have also been developed and demonstrated, and improvement of this FM technology continues. FMD/C write/read technology based on proprietary photochromic substances has been demonstrated in Constellation 3D's laboratories during write/ read/erase/re¬-write experiments
4.3 FMD/C ROM (Read Only) Devices
There are several requirements for the fluorescent materials:
1. The fluorescent ROM material has to be compatible with the substrate material
2. The absorption wavelength should be the same wavelength as commercially
available, low cost semiconductor lasers used in CD players
3. The emitted fluorescent light should be wavelength-shifted by at least 50nm, to allow easy separation of the incident and signal light
4. The material should have high conversion efficiency
5. The material should have the refraction index close to the one of the polycarbonate
6. The material should stay stable over a reasonable time
7. Fast response - lnsec
Light-sensitive material:
The photo-polymer composition (PPC) - is a mixture of monomers and oligomers with photoinitiator, which initiates polymerization process under radiation in the certain spectrum range. PPC serves as substrate for the data carrier, oxazine-1, methylene blue, methylene violet and other red dyes serve as the photo-initiator
Pit filling process: .
The working surface of a polycarbonate disc is a plane with pits - cavities 0,5um in size, located in a certain order. Such micro relief can be filled with liquid monomeric or oligomeric substances that turn into hard polymer substances when subjected to UV light. The substances fill the pits and overflow to form a thicker layer on the media surface. The ratio of layer thickness in pit to its thickness on the surface makes the contrast. One of the main tasks of confronting the scientists in developing the process of filling the pits, creating the overflow and choosing the material, was to find the combination of these that provided the largest such contrast.
4.4 FMD/C Recordable (Write Once Read Many) Devices
In addition to the requirements for ROM media, RECORDABLE media require the following:
A writing process where the writing light is able to turn on or off the fluorescence.
A threshold level above which the fluorescent material is changed by the power level of the write, and below which the material is unchanged during any subsequent read-out. Currently 2 techniques have been developed: Thermal Bleaching:
In this technique the material is initially fluorescent. The incident write light heats the material, destroying the fluorescence. The write parameters are similar to CD/R recording and the standard optical writing 15mW laser is well suited for providing CD-R equivalent data writing rates. Materials suitable for applying this technique for use with red, green and blue laser wavelengths have been developed. ¦Photochemical Reaction:
Materials of this class are initially not fluorescent, and the write light initiates photo-chemical reactions, thereby creating fluorescence. The highly non-linear process associated with this reaction causes an effective threshold. Because no heating is involved, the required write power is low, allowing even light emitting diodes (LED arrays) to be used. With LED arrays, pages of information can be written simultaneously, thereby additionally enabling card applications. Current materials are sensitive to green and violet wavelengths.
4.5 FMC "CLEARCARD" Reader
The block diagram above shows the device for reading data from a Fluorescent Multi-Layer Card (FMC)-"ClearCard". A semiconductor laser produces a beam, which is then focused on a selected layer ofthe card. A cylindrical lens forms a 500x2um line, which by means of a scanning mirror scans across a page area of the card. The induced fluorescent light is imaged to a CCD array. A "frame grabber" receives data from the CCD. In the subsequent image processing step the image is aligned, distortions are
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4.6 FMD Disc Drive
The drives have most components in common with CD/DVD systems: Laser, beam-forming optics, spindle, tracking / focusing actuators, control electronics, data channel, data interface. The only additional components are filters to separate the fluorescent light from laser light, and an optical element to correct for different optical path length in the storage medium, depending on the selected layer. Modifications in the electronics include detector circuit with higher sensitivity and the addition of servo electronics to address different layers within the multi-layer disc. A schematic diagram of a FMD drive is shown.
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5. Industrial Production Prototypes
Constellation 3D, Inc. has developed and proven the basic technology and will continue to develop fully functional prototypes of end-user products. With respect to each of the following products, the company will seek and establish joint ventures with strategic partners having an established market share and manufacturing capability in the relevant product market.
5.1 FMC ClearCard ROM
The planned initial production model is a credit card-sized ClearCard -ROM with up to 20 layers, 400 MB/cm2 data density and up to 10GB capacity* - twice current single-sided DVD disc, but at a fraction of the cost and size. The design of the reader will be simple, with virtually no moving parts, making them resilient to all kinds of shocks. The potential number of applications for which these cards could be used are almost limitless - from e-books and home entertainment systems to e-books and archival and navigational systems. The ClearCard could also be used in many applications where a CD/DVD discs are currently used. The cost of production of these cards is less than $10.
Constellation 3D has recently confirmed in its labs the feasibility of production of a 50.-layer.ClearCard ROM with a storage capacity of 1 Terabyte and data transfer speeds of up to 1 Gigabit/second. The card would be intended for use in HDTV, Video & Music-on-demand and other multimedia applications.
5.2 FMC ClearCard RECORDABLE
The card is a compact version of the FMC ClearCard that enables the user to record the initial information to be stored. The planned initial production model is a credit card sized 10-layer disk with a 1 Gigabyte capacity. It is designed to fit into devices such as laptop and hand-held computers, digital cameras, cellular phones and video recorders and players, for which it will offer light weight, high capacity storage and quick access to data. Next generations of recordable cards will have nearly as much capacity read only cards. For cameras and video players, the ClearCard-RECORDABLE will not only offer the same gains as for laptop and hand-held computers but also offer higher quality video. This technology will be ideal for downloading information from the Internet.
portable
5.3 FMD ROM
This disc takes the CD-ROM & DVD-ROM concept to the next level. The planned initial production model is a 120mm 10-layer disk with 140 Gigabyte capacity - vs. less than 18 Gigabytes for a maximum capacity DVD - giving it the capacity to store up to 20 hours of compressed HDTV film viewing. As mentioned above, existing CD & DVD 120mm disc and drive manufacturing equipment will be adaptable with minimal re-tooling to accommodate the new technology. The new FMD drives will also be backward compatible with (i.e., capable of reading) existing CD & DVD media.
However, it is anticipated that the majority of users will at an early stage decide to take advantage of the much larger capacities and superior performance characteristics of the new FMD discs and make it their media of choice for future data storage applications.
5.4 FMD/C Re-Writable
Re-Writable optical memory carriers have been recently been gaining attention within the optical memory community and provides the maximum amount of flexibility in the determination of data stored at any given time - it is a fundamental requirement of hard disk drives in PCs. In between the two extreme approaches to storing memory, ROM and Re-Writable, are data storage applications where the user requires the flexibility of deciding the initial data to be stored on the media and then the certainty that the data will not later be erased or amended. The initial solution to the most effective data management is FMD/C RECORDABLE storage carriers of very significant capacity. In particular Constellation 3D intends to produce a credit card sized ClearCard -RECORDABLE with 4.7 GBytes capacity and costing under $10, thereby providing users of hand held devices with a cost effective solution to their Internet downloading and other data write-once needs. The next generation products will include genuinely re-writable layers based on most recent development carried out by Constellation 3D.
5.5 Media Manufacturing Technology
Fluorescent media manufacturing process described here utilizes many processes that are typical for CD and/or DVD manufacturing. However, fluorescent media requires many proprietary polymers and compositions that were exclusively developed by Constellation 3D Inc. Company intends to make these materials available to media manufacturers through its selected industry affdiated partners. Media manufacturing process described in this document relies on well known optical disc replication process. Further developments related to increase of data storage capacity to the level of multi-hundreds of gigabytes per disc, will require adoption of other disc manufacturing technologies currently under internal development:
¢ Pre-mastering and mastering process Pre-mastering and mastering processes are very similar to those utilized by CD/DVD industry. However, certain modifications of mastering process will be required (namely glass master and stamper preparation). These modifications are mainly related to pit geometries that are designed to facilitate reliable pit replication and pit filling
¢ Replica manufacturing
Replica manufacturing involves preparation of circular substrates made of low birefringence plastic film (polycarbonate, PMMA or other films with appropriate optical characteristics). Film thickness is between 25 to 30 microns. Prior to usage, substrates are die or laser cut to appropriate diameter (media dependent, see above). Prepared substrate is placed over radial bead of photo-polymer deposited onto nickel matrix top surface (stamper). During spinning process photo-polymer evenly spreads between stamper surface and plastic substrate. Subsequently, UV curing hardens photo¬polymer and now substrate can be separated from top surface of stamper. Substrate contains precise pit geometry. Precision of pit replication exceeds quality of injection-molded substrates (such as CDs or DVDs).
¢ Pit filling
During pit filling, fluorescent dye-polymer evenly spreads over entire replica's informational side by utilizing of spin-coating process (similarly to CD-R dye application). After dye-polymer is UV cured, certain chemical bleaching process is applied to achieve the desired signal contrast ratio of pits and lands
¢ Replica inspection
Each replica is optically inspected to verify proper dye-polymer filling of pits. Such inspection is achieved by observing of emitted light from entire area of data pits by utilizing of CCD camera. At this stage replica is optically inspected for various physical defects such scratches, inclusions and alike
¢ Layer bonding
Layers or replicas are centrally bonded onto optical spacer (0.6 mm thick polycarbonate or PMMA substrate), by utilizing capillary bonding method well known to DVD industry. Since replicas are thin and thus more pliable, formation of air bubbles in the bonding layer is minimized. Requirements to centricity of informational layers are similar to DVD discs (or +/- 25 micron).
¢ Disc decoration
After multiple replicas are bonded on the top of optical spacer (see above), additional Support/protection substrate is bonded on the stack top. These decorated elsewhere substrates are made of solid color inexpensive plastic materials
Fluorescent Multi-layer Memory ¢ Edge sealing
In order to prevent layer separation by physical contact, disc otiter edge is sealed with UV curable photo-polymers typically used for protection of CDs and DVDs.
5.6 FMD/C Advantages
The main advantages of multilayer fluorescent read out are:
1. The multi-layer system is optically transparent and homogeneous.
2. Low absorption in each layer.
3. No absorption for the emitted signal fluorescent light.
4. Lower than CD/DVD sensitivity to imperfections in media and drives. The
fluorescent technique does not depend on interference effects and requires less stringent
manufacturing tolerances for media and drives.
5. The emitted fluorescent light from any given layer is non-coherent, eliminating the problem of parasite interference.
6. The limited lateral spatial resolution for this system is twice that for coherent light based systems (e.g. current CD/DVD reflective systems). In the case of FMD/C, this two-fold improvement over three (3) dimensions, results in an eight-fold improvement in achievable data density.
7. FMD technology is compatible with current CD and DVD formats, having the capacity to handle the same data rates over each of its layers.
The above qualities make FMC unique in its technological capability to facilitate production of a multilayer optical card†ClearCard, in any form factor including postage stamp sized SmartMedia, credit card sized ClearCard, or otherwise. The capacity and speed of reading from these cards can be enormous. For instance, with the level of existing technology ClearCard of 16 cm2 of area with 50 layers can furnish consumers with 1 terabyte capacity and, through parallel access to all its layers, allow over 1 gigabit/sec speed of reading. Another major advantage, for both cards and discs using the technology, is the ability to read data on every layer of the media in parallel, thereby allowing the potential of much grater data transfer rates compared with single layer media. This can be combined with parallel reading from multiple sectors of the same layer to increase data speeds still further, producing 3-dimensional data transfer.
Here is a table demonstrating one of the projects of C3D:50 GB disc (12 layers):
Parameter CD DVD FMD
Disc diameter, mm 120 120 130
Capacity, GBytes -,.64 17,4 50,8
Number of layers i i 2 12
Distance between layers, micron - 40 25±5
Total width of layers, micron 0,11 2 275
Optical system wavelength, nm 780 635-650 532
Distance between tracks, micron 1,6 0,74 0,8
6ž Conclusion
Constellation 3D's fluorescent multilayer optical data storage technology can be utilized to produce compact, removable, inexpensive, rugged, ultra-high capacity data storage devices, having data transfer speeds in excess of lGbit/sec. The company wishes to maintain its focus on research and development in the field of fluorescent multilayer optical storage, with the intention of continually expanding the limits and capabilities of this technology. Having successfully demonstrated prototype multilayer cards and discs incorporating FMC/D technology, the way is now open - through joint ventures with industry leaders to commence industrial production of these devices and take them into the mainstream.
7, FUTURE SCOPE
Dell monitoring advancements in optical technology and expects the cost and performance of CD-RW drives become more competitive with the magnetic formats. Dell plan to offer CD-RW/DVD ROM Combo Drives when reasonably priced. Reliable devices become available. These devices should eventually replace current CD-RW drive and offer convenience, large storage capacity that are backward compatible with previous CD formats, and DVD ROM readability. Dell expects DVD-RAM systems to be adopted by high end users initially. Ram bo systems when available are expected to provide another system in a evolution to a universal RMSD providing a larger capacity drive capable of reading and writing to the most popular CD, DVD format.
Dell is monitoring the development of Blue laser and FMD/FMC technologies for their potential application with existing optical formats. The smaller wavelength of the blue laser may allow data density increase from 3 to 4 times the storage capacity of current optical storage device and a new smaller card format could provide an attractive, high capacity alternative to disk storage. By adding an extra layer and advantages of blue laser second and third generation of disk will be produced of capacity 1000GB.
Bibliography
[l].Ingolf Sander " White Paper on Fluorescent Multilayer Optical Data Storage ",
Constellation 3D, NY, USA [2]. http://vvww.us.net [3]. http://pcstats.com [4]. http://digit-life.com [5].http://dell.com [6]. http://computer.org
CONTENTS
Page
1. INTRODUCTION 01
2. REMOVABLE MEDIA STORAGE DEVICES 02
2.1 Floppy Disk 02
2.2 Optical Formats 02
2.3 CD-ROM 03
2.4 DVD-ROM 03
2.5 DVD-R 04
2.6 DVD-RAM 05
2.7 DVD-RW 05
2.8 +RW 06
2.9 Magneto-Optical Formats 06
2.10 Holographic Data Storage 07
3. FLUORESCENT MULTI-LAYER MEMORY 08
3.1 FMD-ROM: operating principle 10
3.2 FM-disc 12
3.3 FM disc production 13 3.4.FM read devices 15
3.5 Recording on FMD-ROM 15
4. STATUS OF DEVELOPMENT 17
4.1 Media 17
4.2 Fluorescent Material 17
4.3 FMD/C ROM (Read Only) Devices 18
4.4 FMD/C Recordable (Write Once Read Many) Devices 19 . 4.5 FMC "CLEARCARD" READER 19
4.6 FMD DISC DRIVE 20
5. INDUSTRIAL PRODUCTION PROTOTYPES 22
5.1 EMC ClearCard ROM 22
5.2 FMC ClearCard RECORDABLE 22
5.3 FMD ROM 23
5.4 FMD/C Re-Writable 24
5.5 Media Manufacturing Technology 24
5.6 FMD/C Advantages 26
6. CONCLUSION 28
7. FUTURE SCOPE 29
8. BIBLIOGRAPHY 30
