|
In this article:
- Why is Holographic Storage required
- What is Holographic Storage
Why is Holographic Storage Required?
Since the advent, there have been various means and mediums of storing data or information. These devices have been serving us since ages by storing all information directed to them and preserving them for retireval and usage at a later time. Computer storage or memory has seen a barrage of changes over the years. It might br strange today but early computers were more or less without any permanent storage option. It was not before the floppy disks came that ‘storage’ became the buzzword in computer science. The oldest forms of storage were Punched Cards (which also acted as input ‘devices’ at times). These stored information in the form of patterns of holes punched into them (hence the name). When it became difficult to handle these as the amount of information grew large, magnetic storage came to the rescue in the form of magnetic tapes. Magnetic tapes could store information easily and a large amount of it as well. Magnetic tapes were more economical when compared to punched cards. But the area where they lagged behind was speed. Since magnetic tapes allowed only sequential access (information is read one after another even if the information is to be read from the last point), they were very slow when it came to retrieval of information. Thus, new magnetic storage mediums were developed eventually. These were floppy disks and hard disks. Floppy disks revolutionized the transfer of data from one computer to another when no network was present between the two. They became the standard way to store information. Though initially smaller in size, hard disks grew in capacity at an alarming rate and overtook floppy disks by miles in terms of capacity. Optical disks such as CDs and DVDs made it possible to store a huge amount of information in a very less amount of space. They used lasers to write (and read) the information on the medium. Today, computer storage works at blazing speeds while still storing information in huge quantities. But, in a way, we have reached a point where no further advances can be made in terms of capacity of a medium. This is so due to the fact that lasers are a form of light and suffer from the problem of diffraction. This lays down a limit to which data can be concentrated at a place. This calls for a new way to store data which is much more efficient in the use of space and the solution, probably, lies with Holographic Storage.
What is Holographic Storage?
Holographic storage stores information or data on holograms that are made of photopolymers (among other materials). Holographic storage is probably the most promising candidate for becoming the storage medium of tomorrow.
Current storage technologies (e.g. magnetic storage, optical storage etc.) store data on the surface of the medium. This means that the whole of the medium is not utilized and goes waste. Holographic storage changes this trend by using not the surface, but the whole volume of the storage medium. If a particular medium has volume, it means that it can be represented as a 3D object.
Holographic storage is another optical medium of storing data and uses lasers. The laser used in order to read or write data on the medium is comprised of two parts:
- Signal beam
This part of the laser carries the data to be recorded. When the data is to be stored, it is converted into an array (typically, a matrix) by a Spatial Light Modulator (SLM). This array is actually a collection of pixels, some of which are lit and others dark (or off).
- Reference beam
This is the part which actually reads or writes the data. A hologram is created when the two beams intersect as a result of a chemical reaction between the pixels of the signal beam and the light-sensitive medium. These holograms are stored one over another in the volume of the medium (that is, superimposed) by using various angles and wavelengths of the laser.
When data is to be read, the reference beam lightens up the hologram which reveals a pattern of lit and unlit pixels. This is picked up by a reciever or detector that then converts it to data or information.
|
