Optical disc




In computing and optical disc recording technologies, an optical disc (OD) is a flat, usually circular disc that encodes binary data (bits) in the form of pits and lands (where change from pit to land or from land to pit corresponds to binary value of 1, no change, regardless whether in land or pit area, corresponds to binary value of 0) on a special material (often aluminum ) on one of its flat surfaces.

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Surface error scanning

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This section needs expansion . You can help by adding to it. ( July 2020 ) Optical media can predictively be scanned for errors and media deterioation well before any data becomes unreadable. A higher rate of errors may indicates deteriorating and/or low quality media, physical damage, an unclean surface and/or media written using a defective optical drive. Those errors can be compensated by error correction to some extent. Error scanning software includes Nero DiscSpeed , k-probe , Opti Drive Control (formerly "CD speed 2000" ) and DVD info Pro for Windows, and QPxTool for cross-platform. Support of error scanning functionality varies per optical drive manufacturer and model. Error types edit There are different types of error measurements, including so-called "C1" , "C2" and "CU" errors on CDs, and "PI/PO (pairity inner/outer) errors" and the more critical "PI/PO failures" on DVDs. Finer-grain error measurements on CD
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Optical Disc manufacturing

Optical discs are made using replication. This process can be used with all disc types. Recordable discs have pre-recorded vital information, like manufacturer, disc type, maximum speeds, etc. In replication, a cleanroom with yellow light is necessary to protect light sensitive materials and to prevent dust from corrupting the data on the disc. A glass master is used in replication. The master is placed in a machine that cleans it as much as possible using a rotating brush and deionized water, preparing it for the next step. In the next step, a surface analyzer inspects the cleanliness of the master before photoresist is applied on the master. The photoresist is baked in an oven to solidify it. Then, in the exposure process, the master is placed in a turntable where a laser selectively exposes the resist to light. At the same time, a developer and deionized water are applied to the disc to remove the exposed resist. This process forms the pits and lands that represent the data on the
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