HOLOGRAPHIC

PREPARED BY: MANTHAN D SHETH VISHAL R VYAS OVERVIEW

• Devices that use light to store and read data have been the backbone of data storage for nearly two decades.

• It started from CD’s which can store 700MB and has moderate speed.

• Then came DVD which can store up to 17 GB and has speed up to 10 Mbps.

• Recently in 2006 ,BLU-RAY disc was launched which has capacity up to 54 GB and speed of 36 Mbps.

• But looking to the future we need to go ahead and find a better way of storing data, a easier way which is far more better in speed as well as memory.

• In to achieve this scientist have proposed a new technology which uses 3-D layers instead of conventional 2-D. This technology is named HOLOGRAPHIC DATA ST ORAGE STORAGE DEVICES

• To understand clearly the concept of a holographic disc let us have a brief study of the data storage devices which are being used widely today :

• CD

• DVD

• BLU-RAY

NORMAL CD

• Most of a CD consists of an injection-molded piece of clear polycarbonate plastic. During manufacturing, this plastic is impressed with microscopic bumps arranged as a single, continuous, extremely long spiral track of data. CROSS SECTION OF A CD • A CD has a single spiral track of data, circling from the inside of the A label layer disc to the outside. B protection layer

• The elongated bumps that make up C Data layer (reflection layer) the track are each 0.5 microns D protection layer (transparent) wide, a minimum of 0.83 microns long and 125 nanometers high. E Logical 0 (bump) F Logical 1 (pit)

DATA RETRIEVAL

• The data in the cd is stored in these extremely small bumps. The data is retrieved with the help of a red beam in the manner as shown.

• In the first image , we see that the laser (A), reflects (Image 1) on the bump. The reflected laser light however does not seem to reach the sensor (B). The CD-player interprets this as a logical ZERO.

• In the second image we see a reflection on a pit (Image 2). Here we see that the reflected laser light DOES reach the sensor (B). This is being interpreted by the CD-player as a logical ONE.

•The incredibly small dimensions of the bumps make the spiral track on a CD extremely long.

• If we could lift the data track off a CD and stretch it out into a straight line, it would be 0.5 microns wide and al most 3.5 miles (5 km) long. DVD

• are of the same diameter and thickness as CDs, and they are made using some of the same materials and manufacturing methods. Like a CD, the data on a DVD is encoded in the form of small pits and bumps in the track of the disc.

• The elongated bumps that make up the track are each 320 nanometers wide, a minimum of TRACK OF A CD 400 nanometers long and 120 nanometers high

• The biggest advantage of a DVD over a CD is that the pits and the tracks in DVD are smaller so that it takes less space than a DVD to store the same amount of data. Thus physically tighter spacing of pits on a DVD increases its storing capabilities.

TRACK OF A DVD FORMATS IN DVD

• Another big advantage in DVD is that it allows multilayer storing of data on its both sides. The figure shows the way of multistory of data in DVD.

• The microscopic dimensions of the bumps make the spiral track on a DVD extremely long. If we could lift the data track off a single layer of a DVD, and stretch it out into a Format Capacity straight line, it would be almost 7.5 Single-sided/single-layer 4.38 GB miles long! That means that a double-sided, double-layer DVD Single-sided/double-layer 7.95 GB would have 30 miles (48 km) of Double-sided/single-layer 8.75 GB data! Double-sided/double- 15.9 GB layer BLU-RAY DISC • The movie industry has set a revolution with the introduction of Blu-ray Discs (BD) in 2006. With their high storage capacity, Blu-ray discs can hold and play back large quantities of high-definition video and audio, as well as photos, data and other digital content. • Unlike current DVDs, which use a red laser to read and write data, Blu-ray uses a blue laser. • A blue laser has a shorter (405 nanometers) than a red laser (650 nanometers). The smaller beam focuses more precisely, enabling it to read recorded in pits that are only 0.15 microns (µm) long. • Because of this in a Blu-ray the track pitch has been reduced from 0.74 microns to 0.32 microns.

ADVANTAGES OF BLU-RAY DISC OVER CD/DVD • Blu-ray disc can hold more than 25 GB of info -- about five times the amount of info that can be stored on a DVD.

• The speed of this disc is 36Mbps as compared to 10 Mbps of the DVD.

• There is not any much difference between the cost of a blu ray disc and a DVD.

• Record high-definition television (HDTV) without any quality loss

• Instantly skip to any spot on the disc

• Record one program while watching another on the disc

• Create play lists

• Edit or reorder programs recorded on the disc

• Automatically search for an empty space on the disc to avoid recording over a program WHAT IS HDS ??

• Holographic memory will go beneath the surface and use the volume of the recording medium for storage, instead of only the surface area.

• It can store about 1 terabyte (1000 gb) and which has speed about 60 times greater than normal DVDs.

• HDS technology also offers the potential for a 50-year archival lifetime without the expensive environmentally controlled storage required for magnetic tape. Also, the volume of physical space required for archiving data would be reduced substantially.

• HDS could be an enabling technology for high-performance, three- dimensional imaging applications, as well as large image databases, such as those required for satellite imagery and for biometric identification

ADVANTAGES OF HDS • LARGE STORAGE: it can store up to 1 terabyte (i.e. 1000GB)

• HIGH SPEED: Allows a million bits of data to be written and read in parallel with single flash of light. So it has transfer rate greater than 50 Mbps.

• GOOD CLARITY : It has high definition clarity which is even more greater than blu-ray discs.

• REDUCES THREAT OF PIRACY: Because of its unique ability to store data through out the depth of the media,it helps to reduce piracy.

• CHECK AUTHENTICITY: Thus helps in films and game distribution.

• HELPS IN SECURITY: Its random access and data matching abilities help in places like ATM and face recognition systems at airports.