PPT On Holographic Versatile Disc
Holographic Versatile Disc Presentation Transcript:1. Need Of HVD
Multimedia - a single minute of compressed video takes up to 12 Mbytes Data Warehouses - large corporations’ warehouses now taking more than 2 Tbytes World Wide Web - one vendor’s high-end Web server packs 128 Gbytes of disk In Hospitals Multi slice CAT scan: 500MB Cardiac video: 3GB
2. What is HVD ?
Holographic Versatile Disc (HVD) is an optical disc technology which would hold up to 3.9 terabytes (TB) of information . An HVD is an advanced optical disk that’s presently in the development stage. Polaroid scientist J van Heerden was the first to come up with the idea for holographic three-dimensional storage in 1960. Holographic memory systems have been around for decades. They offer far more storage capacity than CDs and DVDs -- even "next-generation" DVDs like Blu-ray -- and their transfer rates are far very less.
3. Basics of Holographic Disk
The first step in understanding holographic disk is to understand what "holographic" means. Holography is a method of recording patterns of light to produce a three-dimensional object. The recorded patterns of light are called a hologram.
4. A Holographic Disk can:
Store information throughout the whole volume of the medium instead of just the surface as with other storage technologies. Uses fewer or no moving parts at all, thus allowing greater data processing speeds. Hold more information than 100 compact disks of the same diameter Can read 64,000 bits at one time, compared to just one or two bits with magnetic storage. Provides unique robustness and error insensitivity
1) Large Data Density/ Capacity Uses optics instead of read-write heads, and uses whole volume of medium instead of just surface as with conventional devices. 2) Better Reliability Uses less moving parts (or no moving parts) 3) High Transfer Rates & Short Access Times Parallel access instead of bit-by-bit access 4) Fault And Damage Tolerance Which Are Not Available Simultaneously With Any Other Storage Technology.
6. HVD Structure
Green writing/reading laser (532 nm) Red positioning/addressing laser (650 nm) Hologram (data) Polycarbon layer Photopolymeric layer (data-containing layer) Distance layers Dichotic layer (reflecting green light) Aluminium reflective layer (reflecting red light)
7. Working Principle HVD
uses a technology called 'collinear holography,' in which two laser rays, one is blue-green and another is red, are collimated into a single beam.. The blue-green laser reads data encoded as laser interference fringes from a holographic layer near the top of the disc while the red laser is used as the reference beam and to read servo information from a regular CD-style aluminium layer near the bottom. Servo information is used to monitor the position of the read head over the disc, similar to the head, track, and sector information on a conventional hard disk drive.
8. HVD Write System
A simplified HVD system consists of the following main components: Blue or green laser (532-nm wavelength in the test system) Beam splitter/merger Mirrors Spatial light modulator (SLM) CMOS sensor Polymer recording medium
9. When the blue-green argon laser is fired, a beam splitter creates two beams. One beam, called the object or signal beam, will go straight, bounce off one mirror and travel through a spatial-light modulator (SLM). An SLM is a liquid crystal display (LCD) that shows pages of raw binary data as clear and dark boxes. The information from the page of binary code is carried by the signal beam around to the light-sensitive lithium-niobate crystal. Some systems use a photopolymer in place of the crystal. A second beam, called the reference beam, shoots out the side of the beam splitter and takes a separate path to the crystal. When the two beams meet, the interference pattern that is created stores the data carried by the signal beam in a specific area in the crystal -- the data is stored as a hologram.
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