02-06-2012, 05:27 PM
Fluorescent Multilayer Disc
Fluorescent Multilayer Disc.ppt (Size: 255.5 KB / Downloads: 113)
INTRODUCTION
Compact discs- revolutionary product-helping hand to both users and programmers.
Followed by DVDs-limitations
the company Constellation3D demonstrates a new format- FMD
concept of the volumetric storage of information.
Data recorded on multiple layers located inside a disc or a card, as opposed to the single layer method available in compact discs, and double layer method available in DVD’s.
When excited by an external light source, the fluorescent material embedded in pits and grooves each layer emits radiation. The information is then decoded as modulations of the intensity and color of the emitted radiation.
OPTICAL STORAGE MEDIA TODAY
CD ROM - intd in 1984 - CD-ROM drives and discs quickly evolved to a low-cost digital storage option because of the established CD-audio industry-Data bits are permanently stored on a CD in the form of physically moulded pits in the surface of a plastic data layer, coated with reflective aluminum. Common data transfer rates are approximately 5 MB/ sec. Faster speeds reduce data access time, but vibration and noise problems limit maximum speeds to approximately 52X.
DVD ROM - intd in 1995- as a result of the consortium of 10 companies -7 times the storage capacity of CDs- DVD-ROM drives rotate the disc more slowly than CD drives, but data throughput is considerably higher because the data density is much greater than on CDs.
FLUORESCENT MULTILAYER DISCS
CDs & DVDs use single & dual metallic layers, respectively, for storage, where a laser beam cannot accurately penetrate the solid, reflective layer where data is stored. In the case of DVD, the laser can penetrate one layer deep to read the second layer, but after that, the laser becomes diffused and unable to read the data clearly.
FMD-ROM is a totally clear disc. Instead of reading a single layer, the data is stored on fluorescent materials in multiple layers, which give off light. Constellation 3D has talked about 10 or more layers per disc. The five-inch disc, which is the same size as CD-ROMs and DVD-ROMs, can hold up to 140GB of data -- almost 30 times the capacity of a DVD-ROM disc.
TECHNOLOGY OVERVIEW
Transparent disc
Principle- PHOTOCHROMISM
An informational element of FM-disc (photochrome) can change its physical properties (colour and fluorescence) under influence of a laser of definite power and wavelength.
When switching on a laser , a photochemical reaction starts which causes fluorescent properties to appear on a photochrome, which initially don’t possess those properties.
The fluorescence is caught up by a photo-receiver and is fixed as a value "1".
TECHNOLOGY OVERVIEW
In case of fluorescent discs the quality of the signal gets affected much slower with increasing number of layers.
According to FMD-ROM developers, even with a hundred layers a useful signal will be acceptable.
They also state that with a blue laser (480 nm) it is possible to increase record density up to tens of Terabyte on one FM disc.
Also features parallel reading.
FMD- SOME FEATURES
Multilayer disc is transparent and homogeneous
Negligible loss of useful signal while passing through several layers
Fluorescence of a separate element easily passes through disc layers
Less sensitivity (than of CD/DVD) to different imperfections of reading devices.
Fluorescent technology does not require special manufacturing conditions
Reflective fluorescent light from any layer is not coherent, it prevents the problem of multiple interferences.
FMD-technology is compatible with CD and DVD formats supporting the same data distribution system on each layer.
CD & FMD PRODUCTION
CDs- As a storage device they use a glass plate covered with a thin photo resistive layer. A laser beam, intensity of which is modulated with digital information, gets into photo resist which causes markings that correspond to bits of digital code. Then the photo resist is developed and covered with a metallic layer. This Master-copy after recording, contains digital information in the form of pits. Then they make exact negative copies by a galvanic way which later serves as a press-matrix. This negative may be used for CD manufacture.
In FMD technology an exact copy of pit is of vital importance. That's why these two technologies differ. Here, a master-copy is a nickel matrix (a stamp). It is a negative copy, like that of CD-technology. An FM disc consists of several layers and that's why the process contains several steps: informational layers are produced separately and then they are combined together.
RECORDING OF FMD ROM
No prototype yet. Still under development
A technology of manufacturing these discs will be the same as for FMD ROM except the fact that they will use another fluorescent material capable of change under the influence of a laser.
While recording one must observe the following rules:-
The power of a laser is sufficient enough to provide an element with fluorescent properties
The threshold power of laser should be used for recording (in order to change fluorescent properties of the material) and for reading less power must be made use of.
FMD RECORDING
The first principle (thermal) implies usage of material that 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 material gets fluorescent properties. There, a low- power laser is enough, or even a usual LED. With the latter (LED matrix) a simultaneous record of the whole array of information is possible.
FMD READ DEVICES
Parallel Reading- this technology allows parallel reading; it means that a sequence of bits is recorded not along a track but deep into layers. That's why we receive three types of data reading: successive, successive-parallel and parallel.
And the reading speed reaches 1 Gigabit/s. We should notice that mechanical speed of the drive is 450 times lower than that of DVD.