How things work CD-ROM

How does CD-ROM burning work?


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How does CD-ROM burning work?

And why is that even called "CD burning" when there is no fire here? Caroline from Viersen wonders why people talk about the CD burner when it's not about heat at all?

A CD-ROM is a data storage medium that can contain all kinds of information in the form of text, images, music or films. A shiny silver plastic disc serves as the data carrier. All information contained on the CD-ROM is stored as a sequence of numbers made up of zeros and ones. All letters, including most of the characters on the computer screen, can be uniquely represented as an eight-digit (8-bit code) string of zeros or ones. Basically everything is translated into zeros and ones by the computer. Music or pictures can also be represented in digitized form with a series of numbers.

These zeros and ones are, so to speak, translated again on a CD-ROM, in a row of tiny depressions in the smooth surface. ("Pits") The layer and the depressions stand for the zeros and each edge of a depression means a one. Overall, the pits form a spiral track.

The CD-ROM player uses a laser beam to read this track. This laser light beam is now directed onto the CD. It starts inside and then pushes itself further and further outwards as you read. If it hits the layer or the bottom of a depression, it is thrown back. If it hits an edge, the beam is deflected. The reflected light is measured with a sensor and the different light intensities trigger corresponding current impulses.

It is basically the same for burned CDs. In addition to the reading beam, a much stronger writing beam is used here. One layer of a blank CD consists of a kind of synthetic resin compound (polycarbonate). If this layer is exposed by the writing beam of the burner, the plastic crystallizes out. This is called burning because the laser produces heat on plastic and burns itself into the areas.

These written or exposed areas are so small that they cannot be seen with the naked eye. During the reading process, the reading beam is refracted and scattered at these exposed and crystallized areas. The reading beam can shine through the plastic at the points that the writing laser of the burner has not irradiated, is reflected, measured and "deciphered".

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