How work optical disk?

Answer 1

We all use optical drives on our computers. However, have you ever wondered how on earth it is possible to store huge amount of data on a CD (compact disc) or DVD (digital video disc) or how an optical drive such as a CD ROM drive works? Read on if you are interested to know.

Anoptical disc such as a CD or a DVD has basically 3 layers on it. The non-silvered side is the layer on which you can affix a label on the CD for identification of its contents. It also serves to protect the data on the disc. The middle layer is the reflective layer. It is sandwiched between the non-silvered layer and the silvered layer on the other side of the disc. The reflective layer is the one that stores all the data in microscopic pits in grooves on an optical disc.

This is why a slight scratch on the silvered surface of a CD does not entirely damage its property to store and display data. However, what the scratch does is to impede data reading on an inserted CD by blocking the beam of light from a laser on the optical drive. This is also one reason it is recommended for you to use a soft marker for writing the label description on the non-silvered side of the CD.

A DVD is an improved version of an optical disc that enables you to store significantly more data on it than is possible to store on a CD. While a CD can store upto 700 MB (megabytes) of data on it, a single layer DVD can store 4.3 GB (gigabytes) of data on it. A double layered DVD can store 8.7 GB of data on it.

As opposed to a single layer optical disc which has only one reflective layer, a dual layered optical disc has two reflective layers. The top reflective layer is semitransparent to allow the laser on the optical drive to read the data on the inner reflective layer by a change of focal length.

While you use Nero or other burning software to burn the data on the reflective layer on a CD or DVD inserted in the respective CD or DVD writer optical drive, mass-produced commercial software is not burned on optical discs that way because there exists a quicker method. It involves the use of a mold to stamp press the data in pits on the reflective layer in an optical disc.

When you insert a data CD or DVD in a CDROM or DVDROM drive, a laser on the optical drive focuses a beam of light on the reflective layer on the optical disk. The beam focused on pits is scattered, whereas that on lands is reflected back with higher intensity and stored in a photo diode array. The diode array is used to read and analyze the data. CDROM optical drive technology is now obsolete and has given way to DVDROM optical drive technology.