How are read / written optical disks

ianuarie 23, 2013

One of the biggest breakthroughs in storage technology is the optical storage. The basis of this type of storage is optical phenomenon known as light reflection. 1 The fact that two objects can reflect light differently,  is used by the optical storage technology to represent a number of bits in a reflective surface.

Next is to find out some details about how data storage using optical technology. In other words, you’ll learn why an optical medium is optical, not magnetic.


Optical media stores data in a layer of photosensitive storage along a spiral track. (For a compact disc, such a track would reach a length of approximately 5 km.)

Compozitie CD

Order bits are registered on the space marked by a cross in the form of microscopic cavities or dots that are designed differently to reflect light emitted by a laser beam. A flat surface means 0 (land) and a cavity or point 1 (pit).
Points that represent bits size and the distance between them is oridinul microns. (A micron is equal to a thousandth of a millimeter – 10 -6 meters). At Micron, density of points that can be represented is hundreds of millions on an area of ​​a few square centimeters.

Comparatie CDvsDVDvsBlu-ray

The laser beam

To decode billions of points inside the data storage layer is used a laser beam.

Laser bluray

Beam verifies the absence or presence of serial microscopic cavities or points that represent bits and report the electronic signals as the absence or presence of the world. Further reading electronic unit interprets electronic signals received as bytes.

Raza laser

The advantages of optical storage

The most common optical media (CD and DVD) weighing a few grams, with a thickness of 1.2 mm and a diameter of 12 cm.

Direct access to stored information.
Any information can be found in the storage area of ​​an optical medium within measurable in milliseconds.

Improved security of data stored and long use

Optical storage media not by reading wear. In terms of handling carefully the information stored on an optical disc (quality) can be accessed for ten years.

Low price per storage megabaitul
A regular media (CD or DVD) can be purchased for a ridiculously low price, and provides a relatively large storage capacity.


Most optical storage media fall WORM storage media category – Write Once Read Many.

WORM medium that can be written once is closely related to the process of writing data, which is irreversible. Storage layer once it has been modified by writing data can not be brought to its original condition.

The fact that the stored information can not be deleted or modified should not be seen as a major disadvantage. Feature information permanently prevents accidental deletion or modification thereof.

Non-optical media Worm, rerecord called, can also be read many times but at the same time can be erased and rewritten with new information.

  1. Reflection, reflections, sf 1. Phenomenon of partial return of light, sound, radiation in the environment from which they came when they encounter a surface separating two media, reflection


Nelamuriri? Intrebari?

Intreaba sau cauta raspunsul la sectiunea de intrebari si raspunsuri.