How do CDs/DVDs/game disks work?
In: Technology
All computer data ultimately breaks down into a series of ones and zeros. This gets represented on an optical disk (CD/DVD/Blu-Ray/etc) by a series of pits and bumps in the surface of the disk, almost like a vinyl record. Those pits and bumps are under a clear sheet of polycarbonate on the disk (so you can’t feel them).
To read them, a laser (a highly focused beam of light) is run along the disk and the deflection (or not) of the beam is read as a 1 or a 0. The primary differences in the different types of media are the wavelength of the laser, which allows data to be stored more closely together on the physical disk. In some cases, the data can actually be written in two or more layers on the disk and the beam is focused on different depths in the surface of the disk to read them.
The shiny layers on the disks have tiny groves cut into them in circles around the center. These groves are only a few hundred nanometers wide which is just wide enough for a laser beam. So the disk reader have a laser shining at this grove and a detector that detects the reflection of the laser. This means that it can detect where the grove is cut and where the reflective surface is left intact as the disk spins around. This forms a pattern of ones and zeroes that gets converted into data for the rest of the machine to read.
On the shiny part there are very tiny pits and valleys that each represent a bit. The disc reader then interprets them as data.
Latest Answers