h Holographic
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Transcript of h Holographic
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MAGNETIC STORAGE WITH LIMITEDSPACE
LESS MOBILITY
EXPENSIVE
SLOW TO ACCESS
MOBILE STORAGE WITH VERY LESS
STORAGE
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With the technological advancements thestorage even advanced for more reliableand better media for the permanent
storageThe magnetic storage devices are mostly
used but they are more prone to
corruption.So to avoid that the losses due tocorruption special data is stored in someother media.
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1.CD
2.DVD
3.BLU-RAY DISC
4.HVD*
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CD (commonly stands for compact disc) is oneof the oldest and most commonly used opticalmedia for storage.
It is generally of a standard size of with 8cmdiameter but a mini-CD is now available with alesser diameter and a storage capacity of just250Mb.
A normal CD of 12cm diameter has a storagecapacity of 700Mb of data
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DVD (also known as Digital Versatile Disc or DigitalVideo Disc) is a popular optical disc storage mediaformat. Its main uses are video and data storage. Most
DVDs are of the same dimensions as compact discs(CDs) but store more than six times as much data.
Variations of the term DVD often describe the way data isstored on the discs: DVD-ROM has data which can onlybe read and not written, DVD-R and DVD+R can only
record data once and then function as a DVD-ROM. DVD-RW, DVD+RW and DVD-RAM can both record and erasedata multiple times.
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DESIGANATION SIDES
LAYERS
DIAMETER(cm)
CAPACITY(Gb)
DVD 1 SS SL 1 1 8 1.46
DVD 2 SS DL 1 2 8 2.66DVD 3 DS SL 2 2 8 2.92
DVD 4 DS DL 2 4 8 5.32
DVD 5 SS SL 1 1 12 4.
DVD 9 SS DL 1 2 12 8.54
DVD 1 DS SL 2 2 12 9.4
DVD 14 DSDL/SL
2 3 12 13.24
DVD 18 DS DL 2 4 12 1 . 8
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Blu-ray Disc (also known as Blu-ray or BD) is an opticaldisc storage medium. Its main uses are high-definitionvideo and data storage. The disc has the same physicaldimensions as standard DVDs and CDs.
The name Blu-ray Disc is derived from the blue laser(violet-coloured) used to read and write this type ofdisc. Because of the beam's shorter wavelength (405nanometres), substantially more data can be stored ona Blu-ray Disc than on the DVD format, which uses a
red (650 nm) laser. A two-layer Blu-ray Disc can store50 gigabytes, almost six times the capacity of a two-layer DVD, or twelve and a half times that of a single-layer DVD.
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TYPE PHYSICALSTATE
SINGLE LAYERCAPACITY
DUAL LAYERCAPACITY
STANDARDDISC SIZE
12 cm, singlesided
25 GB 50 GB
MINI DISC SIZE 8 cm, single sided 7.8 GB 15.6 GB
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Blu-ray Disc uses a BLUE (technically violet) laser operating at awavelength of 405 nm to read and write data. Conventional DVDsand CDs use red and near infrared lasers at 650 nm and 780 nmrespectively.
The blue-violet laser's shorter wavelength makes it possible to
store more information on a 12 cm CD/DVD sized disc. Theminimum "spot size" on which a laser can be focused is limited bydiffraction, and depends on the wavelength of the light and thenumerical aperture of the lens used to focus it. By decreasing thewavelength, increasing the numerical aperture from 0.60 to 0.85and making the cover layer thinner to avoid unwanted opticaleffects, the laser beam can be focused to a smaller spot. This
allows more information to be stored in the same area. For Blu-rayDisc, the spot size is 580 nm. In addition to the opticalimprovements, Blu-ray Discs feature improvements in dataencoding that further increase the capacity
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FOR
DRIVESPEED
DATARATE
WRITE TIME(MIN)
MB/S SL DL
.
2 2. 4
4 .4 2
8. 8
8 .8 8 4
2 .22 . 4
8 24.
2 2 . 4
FOR B -RAY
DRIVESPEED
DATARATE
WRITE TIME(MIN)
MB/S SL DL
4. 8
2 . 4
4 8 2 4
2
8 2 2
2 4 8
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1. Green writing/reading laser (532 nm)2. Red positioning/addressing laser (650 nm)
3. Hologram (data)4. Polycarbonate layer5. Photo polymeric layer (data-containing layer)6. Distance layers
7. Dichroic layer (reflecting green light)8. Aluminum reflective layer (reflecting red light)9. Transparent baseP. PIT
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THE OPTICAL STORAGE MEDIA IS ABETTR,SAFE,RELIABLE,FAST AND CHEAPWAY OF STORING DATA.
THEY HAVE TAKEN OVER THE MAGNETICSTORAGE FOR BACKING UP OF DATA AND
FUTURE PROSPECT OF STORING DATA INOPTICAL DEVICES IS VERY IMPRESSIVE
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