CDs and DVDs and Blu-ray, oh my!īecause CDs deal with digital data, they’re not limited to just storing music and audio. In this way, the playback device receives all the digital data it needs to reconstruct the sound and music you hear on your speakers or headphones. Whenever the laser light reflects back up, a photoelectric cell is there to detect it and generates a binary ‘one’ while sending out binary ‘zeros’ when nothing comes through (as is the case with the scattered light coming from pits). Those untouched lands on the disc’s surface will reflect the light back up, while pits cause the light to scatter. A small motor spins the disc at high speed and a semiconductor diode laser begins scanning along the shiny underside. A completed master can then be used to print out a massive number of plastic discs, which each receive a thin layer of aluminum (to reflect light), protective coatings, and finally the top label.Įven more magic happens once one of these discs goes inside a CD player. This microscopic process happens around and around the disc in a long spiral containing tens of billions – yes, tens of billions – of these pits! If straightened out, this spiral would stretch for miles. A laser is used to transfer digital data (a long sequence of ones and zeros) to this disc by literally burning small ‘pits’ into the surface, with untouched areas (called ‘lands’) representing ones and burned areas representing zeros.
Let’s start at the beginning of the manufacturing process, in which a ‘master’ version of a disc is created. When it comes to CDs, lasers perform two very important functions: reading data and writing data.
It was truly a game changer, but back to the important part – where exactly do the lasers come in? Reading and writing Discs shouldn’t wear out as long as they don’t get scratched, and it’s much quicker to skip between different tracks on an album, not to mention all the benefits that come with storing audio as digital data rather than analog. CDs eliminated any direct contact between the storage medium and the playback device by using a low-power laser instead. These analog formats are prone to physical damage, interference, and wear out over time, which negatively affects sound quality. Lasers are especially useful because they emit a super-focused beam of light that can be used in some really sophisticated ways, from laser cutting and printing to fiber optics and surgery.īefore the invention of the first CD, the most common methods of storing music were vinyl records and magnetic cassette tapes. If you have a fiber-optic internet connection for example, you’re actually taking advantage of light and its ability to travel through long glass or plastic fibers without hitting the same kind of interference that regular electrical signals do when traveling through metal cables. Lasers are light, but betterĪll compact discs depend on something called optical technology, which covers anything related to light being applied in a certain way to accomplish something. Let’s explore how this whole process works, as well as how optical media has evolved over time. Lasers are also used to get all of that information onto the disc in the first place. These thin discs have been around for a while and maybe aren’t quite as revolutionary as they used to be-but did you know that there are lasers involved?Įvery time you’ve popped one of the above into your computer, DVD player, or video game console, a small beam of light is being used to grab digital data directly from the disc’s surface and convert it to music you can hear and images you can see.
Illustration: Liz Xiong CDs, DVDs, Blu-ray.
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