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Optical Discs are storage devices, in which the data is stored in the form of Binary values. The writing is carried out either optically or mechanically and reading is done using Laser Beams. Based on the technology used to manufacture and read write process, there are different types of Discs like CD, DVD, Blu-ray etc. Optical discs store much more data than Magnetic Storage Devices. Optical discs were invented by David Paul Gregg in 1958 for video recording. Optical discs are mainly made of Plastic and Poly Carbonate material.
The binary data is written into the Disc in the form of PITs (Binary Value ‘0’) and LANDs (Binary Value ‘1’). The reading is done from outer side to inner side and the writing is done from inner side to outer side. Mainly the frequency of PITs and LANDs decides the storage space in the disc. If we are using high frequency lights like Blu-ray Laesr, we can read and write more binary numbers from and into a single disc.
Compact Disc (CD)
These kind of discs are mainly used for storing music and Software packages. The typical storage is 760 MB. There are different versions available for these kinds of discs. They are CD-R (ROM), CD-RW (Re-Writable). The typical wavelength of the laser beam used to read the data from the CD is 780nm.
Digital Versatile Disc (DVD)
These kind of discs are mainly used for storing movies and Games. The typical storage is 4.7 GB. In DVD also there are different versions available ike DVD-R, DVD-RW etc. The typical wavelength of the laser beam used to read the data from the DVD is 650 nm.
Blu-Ray Disc (BD)
These are the latest improvement in Optical Discs. They are mainly used to store High Definition Movies, Games with High Graphics or to store more than one movies in a single disc. Watching contents from these kind of discs will provide a theatrical experience to the audience. The typical storage space in a Blu-Ray disc is about 25GB. The typical wavelength of the laser beam used to read the data from a Blu-ray disc is 405 nm.
The main disadvantages of Optical disc is that they are made of thin plastic material which is not protected with a case. Hence it is prone to Mechanical deformation, dust, scratches etc.
However, Optical discs are light weight with more storage density and immune to Electro Magnetic interference. The storage density can be improved using multi layered recording in which more than one layer is used to record the data.