Docstoc

holographic memory (PowerPoint)

Document Sample
holographic memory (PowerPoint) Powered By Docstoc
					Prepared By :
  DEFINITION

 Holographic memory is a technology that can store
  information at high density inside crystals or
  photopolymers.

 Conventional memories use only the surface to store the
  data. But holographic data storage systems use the
  volume to store data. It has more advantages than
  conventional storage systems. It is based on the principle
  of holography.

 Unlike magnetic storage mechanisms which store data on
  their surfaces, holographic memories store information
  throughout their whole volume. After a page of data is
  recorded
  INTRODUCTION
>>Devices that use light to store and read data has always become the
  backbone of our data storage system for nearly two decades. Each
  time you access towards the large repository of digital information
  the harddisc the mainstay of personal and digital information has
  always Obeyed the law.

>> The rate of advancement in storage technology has been truly
   amazing. From the first instance of digital storage with IBM’s 5 MB
   RAMAC hard disk drive invented in 1956, all the way to the mammoth
   180 GB hard disk drives available today, there has been a 36,000-fold
   increase in storage capacities over the last 50-odd years. However, we
   are fast approaching the physical limit for storing information on media
   such as the magnetic platters of hard disks or the chemical layers in
   optical devices such as CDs and DVDs.

>> With the promise of tomorrow's operating systems incorporating
  stunning graphical interfaces that offer truly immersive virtual reality
  and next generation games that will blur the line between fiction and
  reality, the demands of being able to quickly store and retrieve
  enormous quantities of data are ever increasing.
   BASIC PRINCIPLE OF HDSS
>>A hologram is a block or sheet of photosensitive material which records the
  diffraction of two light sources.

>>To create a hologram, laser light is first split into two beams, a source beam
  and a reference beam. The source beam is then manipulated and sent into the
  photosensitive material .Once inside this material, it intersects the hologram.
  Once a hologram is recorded it can be viewed with only the reference beam.
  The reference beam is projected into the hologram at the exact angle and it
  was projected during recording.

>> When this light hits the recorded diffraction pattern the source beam is
   regenerated out of the refracted light. An exact copy of the source beam is
   sent out of the hologram and can be read by optical sensors. For example a
   hologram that can be obtained from a toy store illustrates this idea. Precise
   laser equipment is used at the factory to create the hologram..
BASIC COMPONENTS OF HDSS

>> BLUE-GREEN ARGON LASER
>>POLARIZING BEAM SPLITTERS
>>MIRRORS TO DIRECT THE LASER BEAMS
>>SPATIAL LIGHT MODULATOR (SLM)
>> LENSES TO FOCUS THE LASER BEAMS
>> PHOTO POLYMER
>>CHARGE-COUPLED DEVICE (CCD )
In a holographic memory device, a laser beam is split in two,
and the two resulting beams interact in a crystal medium to
store a holographic recreation of a page of data.
   WORKING OF HDSS
  RECORDING DATA ON MEDIUM

>>Light from a single laser beam is split into two beams, the signal
  beam (which carries the data) and the reference beam. The
  hologram is formed where these two beams intersect in the
  recording medium. The object beam, gets expanded so that it
  fully illuminates a spatial light modulator (SLM)

>>The object beam finally interacts with the reference beam inside
  a photosensitive crystal causing a holograph to be stored
  READING DATA FROM HOLOGRAM
>>When reading out the data, the reference beam has to hit the crystal
  at the same angle that's used in recording the page. To read out the
  data, the reference beam again illuminates the crystal. The stored
  interference pattern diffracts the reference beam's light so that it
  reconstructs the checkerboard image of the light or dark pixels.

>> The image is directed upon a charge-coupled device (CCD) sensor
   array that reads the data in parallel, and it instantly captures the
   entire digital page. The binary information can now be read from
   this CCD and the originally stored data is retrieved. This parallel
   read out of data provides holography with its fast data transfer rates
   MULTIPLEXING
>>The method of storing multiple pages of data in the
  hologram is called multiplexing.

  WAVELENGTH MULTIPLEXING
  ANGULAR MULTIPLEXING
  SPATIAL MULTIPLEXING
> PERISTROPHIC MULTIPLEXING
> SHIFT MULTIPLEXING
  PHASE ENCODED MULTIPLEXING
MULTIPLEXING COMBINATIONS
ERROR CORRECTION
RECORDING ERRORS

>>When a laser beam is split up (for example, through a SLM), the generated
light bleeds into places where light was meant to be blocked out. Areas where
zero light is desired might have minuscule amounts of laser light present
which mutates its bit representation. For example, if too much light gets
recorded into this zero area representing a binary 0, an erroneous change to a
binary 1 might occur.

PAGE-LEVEL PARITY BITS
>>When a page of data is written to the holographic media, the page is
separated into smaller two dimensional arrays. These subsections are
appended with an additional row and column of bits. The added bits calculate
the parity of each row and column of data. An odd number of bits in a row or
column create a parity bit of 1 and an even number of bits create a 0 .
  INTERFACING

>SMART INTERFACING
>>Smart interfacing is a method of controlling the way data
  is sent to the processor from the holographic memory by
  a predefined set of logical commands.
>INTELLIGENT INTERFACING
>>intelligent interfacing is different in one important way.
  Intelligent interfacing has external control signals which
  can be manipulated to transform incoming data in a non-
  static manner.
  IMPLEMENTATION
>>Photorefractive crystals are suitable for random
  access memory with periodic refreshing of data
  and can be erased and written many times.
  Photo polymers have been developed that can
  also be used as a holographic storage medium.

>>An example of photo polymer is Dupont’s HRF-
  150. This film can achieve 12bits/µm2 with a
  100µm thickness, which is grater than DVD-ROM
  by a factor of two.

>>Stored holograms are permanent and do not
  degrade over time or by read out of the
  hologram, so photopolymers are suited for ROM.
 ADVANTAGES OF HDDS
>> With three-dimensional recording and
  parallel data readout, holographic memories
  can outperform existing optical storage
  techniques. In contrast to the currently
  available storage strategies, holographic
  mass memory simultaneously offers high
  data capacity and short data access time
  (Storage capacity of about 1TB/cc and data
  transfer rate of 1 billion bits/second).

>> While a defect in the medium for disk or
  tape storage might garble critical data, a
  defect in a holographic medium doesn't wipe
  out information
  DISADVANTAGES OF HDDS
>> Manufacturing cost HDSS is very high and there is a
  lack of availability of resources which are needed to
  produce HDSS.

>> A difficulty with the HDSS technology had been the
  destructive readout. The re-illuminated reference
  beam used to retrieve the recorded information, also
  excites the donor electrons and disturbs the
  equilibrium of the space charge field in a manner
  that produces a gradual erasure of the recording.

>> You would be unable to locate the data if there’s an
  error of even a thousandth of an inch.
  POSSIBLE APPLICATIONS
>> Holographic memory systems can potentially provide the high
   speed transfers and large volumes of future computer system.

>>One possible application is data mining. Data mining is the
   processes of finding patterns in large amounts of data. Data
   mining is used greatly in large databases which hold possible
   patterns which can’t be distinguished by human eyes due to
   the vast amount of data.
>> The many advances in access times and data storage capacity
   that holographic memory provides could exceed conventional
   storage and speedup data mining considerably

>> Another possible application of holographic memory is in
   petaflop computing
Holographic Versatile Disc (HVD) is
an optical disc technology still in the
research stage which would hold up
to 3.9 terabytes (TB) of information

The Holographic Versatile Card (HVC)
is a data storage format by Optware;
the projected date for a Japanese
launch is 1st half 2007




                                          Holographic Versatile
                                          Card
Holographic Versatile Disc structure
1. Green writing/reading laser (532 nm)
2. Red positioning/addressing laser (650 nm)
3. Hologram (data)
4. Polycarbon layer
5. Photopolymeric layer (data-containing layer)
6. Distance layers                                   Picture of a HVD by Optware
7. Dichroic layer (reflecting green light)
8. Aluminium reflective layer (reflecting red light)
9. Transparent base
 CONCLUSION
>> The future of HOLOGRAPHIC DATA STORAGE
  SYSYEM is very promising. The page access of data
  that HDSS creates will provide a window into next
  generation computing by adding another dimension
  to stored data

>> It will most likely be used in next generation
  supercomputers where cost is not as much of an
  issue.

>> However, many advances in optical technology and
  photosensitive materials need to be made before we
  find holograms in our computer systems

				
DOCUMENT INFO
Shared By:
Categories:
Tags:
Stats:
views:49
posted:1/30/2012
language:English
pages:21