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Optical storagе

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Simple description of how cd and dvd are recorded.

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Optical storagе

  1. 1. Definition of optical storage Optical storage is a term from engineering referring to the storage of data on an optically readable medium. That sort of mediums are: DVD (Digital Versatile Others like:CD (Compact disc) Disc or Digital Video Disc)
  2. 2. Optical disc drive (ODD)An optical disc drive is a disc drive that uses laser light or electromagnetic waves near the light spectrum as part of the process of reading or writing data to or from optical discs.
  3. 3. Laser and optics In an ODD there is an optical path, placed in a pickup head consisting of semiconductor laser, a lens for guiding the beam, and photodiodes detecting the light reflection from discs surface.Laser assembly in a CD burner:
  4. 4. How do we read data?CDs store information in series of 0s and 1s. These 1s and 0s are represented by millions of tiny bumps and flat areas on the discs reflective surface.
  5. 5. How do we encode data?A recorder encodes (or burns) data onto a recordable CD-R, DVD-+R, or BD-R disc (called a blank) by selectively heating parts of an organic dye layer with a laser. It changes the reflectivity of the dye by making marks.
  6. 6. Types of media1. Read Only Media (ROM)2. Rewritable media - CD-RW, DVD-RW,DVD+RW, DVD-RAM and BD-RE3. Double-sided media4. Double layer (DL) media
  7. 7. Rotational mechanismThe CD player spins the disc whilemoving the laser assembly outward fromthe middle. To keep the laser scanningthe data track at a constant speed, theplayer must slow the disc as theassembly moves outward.
  8. 8. Loading mechanismsTray-loading mechanism:Slot-loading mechanism:Top-loading mechanism:
  9. 9. Recording performanceOptical recorder drives are often marked with three different speed ratings. In these cases, the first speed is for write- once (R) operations, second for re-write (RW or RE) operations, and one for read-only (ROM) operations. The Z-CLV recording strategy:
  10. 10. Example:For example a 12x/10x/32x CD drive is capable of writing to CD-R discs at 12x speed (1.76 MB/s), write to CD-RW discs at 10x speed (1.46 MB/s), and read from any CD discs at 32x speed (4.69 MB/s).
  11. 11. New technologyBlu-ray Disc (also known as Blu-ray or BD) is an optical disc storage medium designed to supersede the standard DVD format. Its main uses are for storing high-definition video, PlayStation 3 games, and other data, with up to 25 GB per single layered.
  12. 12. Recorder Unique Identifier Owing to pressure from the music industry, as represented by the IFPI and RIAA, Philips developed the Recorder Identification Code (RID) to allow media to be uniquely associated with the recorder that has written it.Example:Security Identification Code - 12345678Recorder Identification Code - 87654321 PHI (for Phillips)
  13. 13. Contents1. Definition of optical storage2. Optical disc drive (ODD)3. Laser and optics4. How do we read data?5. How do we encode data?6. Types of media7. Rotational mechanism8. Loading mechanisms9. Recording performance10. New technology11. Recorder Unique Identifier
  14. 14. That was all!Thank You for Your patience and attention. Author of the presentation: Georgi Mirchev 1b Group

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