Compact Disc Manufacturing

Written by Abby Luttrell
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For anyone who may think that CD replication is easy and foolproof, here are a few facts about compact disc manufacturing. A CD is a thin plastic disc, as you know. What you may not know is that information is encoded in a plastic encased spiral track contained on the top of the disc.

This spiral track is read optically by a noncontact head which scans the disc as the disc spins. The disc is scanned from the inner center hole towards the outside edge, which is why the frequency of rotation decreases as the scanning progresses. The spiral is scanned at a constant rate to ensure a constant flow of data.

Possible Flaws in Compact Disc Manufacturing

Here's where flaws and faults in cheap CD replication can become nightmares with an unreliable CD replication service. In compact disc manufacturing, the spiral track contains shallow depressions known as pits. The space between the pits is known as "land". Binary information is encoded by the distance between the pits and the land.

A low power laser beam from the optical head is focused on the spiral layer. As that beam is reflected back into the head, it varies depending on whether the beam is hitting a pit or a land element. This modulated reflected light is converted to a radio frequency. Whew! That's a lot of information, but it shows you why one little glitch or imperfection, an eroding of one of the "pits" or "lands", can result in a dramatically altered and low-quality CD after duplication. That's why you need to get your CDs duplicated with only the most reputable, recommended CD replication service.

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