Compact Disc Terminology

This page contains a list of terms and definitions which are commonly used in the CD and DVD industry. For a detailed list of terms related to computers in general, please visit our Computer terminology glossary page.

BLock Error Rate. This is the "raw" digital error rate before any error correction.
The maximum number of BLERs allowed on a disc. According to the industry standard, a CD-ROM is allowed a BLER of up to 220 before it is considered a "bad" disc.
Compact Disc, a digital medium formed of a 12cm polycarbonate substrate, a reflective metalized layer, and a protective lacquer coating. The physical format of CDs is described by the ISO9660 industry standard. CD-Recordable discs also have an organic dye data layer between the substrate and the metal reflective layer.
Compact Disc-Recordable. This term is used to describe the technology of recordable CD as well as the equipment, software and media used to make recordable discs.
This is a measure of the amount of interference coming from neighboring pit tracks on a CD. As track pitch is tightened (when tracks are packed closer together to put more data on a disc), cross-talk increases. A maximum value of 50% is allowed by Red Book specifications.
One type of organic dye used to form the data layer in CD-R discs. Cyanine was the first material used for these discs, but presently a metal-stabilized cyanine compound is generally used instead of "raw" cyanine. An alternative material is phthalocyanine.
data layer
In CD-R, the organic dye sandwiched between the polycarbonate substrate and the metalized reflective layer of the media. >CD-Recordable discs do not have any data on them until they are recorded. Instead the recording laser selectively melts "pits" into the dye layer -- but rather than burning holes in the dye, it simply melts it slightly, causing it to become non-translucent so the reading laser beam is refracted rather than reflected back to the reader's sensors. In pressed CDs, the data layer is part of the polycarbonate substrate, and is pressed into the top side of it by a "stamper" during the injection moulding process.
injection moulding
A manufacturing method where molten material is forced into a mold, usually under high pressure, and then cooled so the material takes on the shape of the mirror image of the mold.
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lacquer spincoat
Acrylic lacquer is spincoated in a thin layer on top of the metal reflective layer of a CD to protect it from abrasion and corrosion. Usually a decorative label is also applied on top of the lacquer, but this is not a standard requirement.
Mastering is the process of creating a stamper or set of stampers to be used in the injection moulding stage of manufacturing compact discs. During this process a digital signal from a computer is used to guide a laser beam which etches a pattern of "pits and lands" (in the case of CDs) or a continuous groove (for CD-Rs) onto a highly polished glass disc coated with photoresist. This "glass master" is then cured (developed) with ultraviolet light and rinsed off, and a metal (nickel or silver) mold is electroformed on top of it. This mold is removed and then electroplated with a nickle alloy to create one or more stampers to be used in the injection moulding machine to press the data into the polycarbonate substrate of CDs, or the guiding groove into the substrate of CD-Rs.
media or "blanks"
CD-Recordable media are the discs used to record digital information using a special recorder and premastering software with a computer. These discs are made of a polycarbonate substrate, a layer of organic dye, a metalized reflective layer, and a protective lacquer coating. Some discs also have an additional protective coating over the metalized layer, and some discs have a printable surface silkscreened on them.
Orange Book
The Orange Book is the specification for CD-Recordable.
organic dye
The data layer of CD-R discs is made from either cyanine or phthalocyanine dye which is melted during the recording process. Where the dye is melted, it becomes opaque or refractive, scattering the reading laser beam so it is not reflected back into the reader's sensors. The difference between reflected and non-reflected light is interpreted by the player as a binary signal.
An organic dye used to form the data layer in some CD-Recordable discs. Mitsui Toatsu Corporation holds the patent on this dye, but has licensed its formula to some other manufacturers.
pits & lands
In a "pressed" or mass-replicated CD, the bumps and grooves that represent the binary data on a disc's substrate are pressed into it during manufacture. CD-R discs do not have true pits and lands, but the unmelted, clear areas and melted, opaque places in the dye layer fulfill the same function as pits and lands on a pressed disc.
reflective layer
The metal layer on top of the dye that reflects the laser beam back to the reading assembly. This is usually 24K gold in CD-Recordable discs, but Mitsubishi has recently introduced a silver disc as well.
The data-bearing removable "die" used during the injection moulding of a CD to imprint pits and lands into the polycarbonate substrate of the disc. In manufacturing CD-R media, instead of pits and lands, a continuous spiral is pressed into the substrate as a guide to the recorder's laser. The stamper is part of a "disc family" created in the mastering process.
The optical-quality, injection moulded optical-quality clear polycarbonate plastic "bottom" of a CD or CD-R. For CD-Rs, this layer does not contain "pits and lands" but has a single spiral groove that guides the recorder's laser.

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