CD recorder

From Academic Kids

A CD recorder, CD writer or CD burner is a compact disc drive that can be used to produce discs readable in other CD-ROM drives and audio CD players. They are generally used for small-scale archival or data exchange, being slower and more materially expensive than the moulding process used to mass-manufacture pressed discs.

The recorder burns—or encodes—data onto blank CD-R media by selectively heating parts of an organic dye subtrate in the disc with a laser in its write head. This changes the reflectivity of the dye, thereby creating marks that can be read as with the "pits" and "lands" on pressed discs. The process is permanent, and hence CD-R media can be written to only once.

For CD-RW media, the laser is used to melt a crystalline metal alloy in the recording layer of the disc. Depending on the amount of power applied, the substance may be allowed to melt back into crystalline form or left in an amorphous form, enabling marks of varying reflectivity to be created. Most CD-RW media is rated by manufacturers at up to 1000 write/erase cycles.

Contents

Compatibility

Pressed disc CD-R CD-RW
Audio CD player Read Read 1 Read 2
CD-ROM Read Read 1 Read 2
CD-R recorder Read Read/write Read
CD-RW recorder Read Read/write Read/write
DVD-ROM Read Read 3 Read 3
  • Note 1: Some types of CD-R media with less-reflective dyes may cause problems. Phthalocyanine-based discs are said to work best.
  • Note 2: May not work in non MultiRead-compliant drives.
  • Note 3: May not work (http://www2.osta.org/osta/html/cddvd/intro.html) in some early-model DVD-ROM drives.

Performance

Earlier-model recorders were CLV (constant linear velocity) drives. When recording, the spindle motor in the drive would slow as the write head approached the outer rim of the disc to keep the transfer rate constant. The recording speed in this case was rated in multiples of 150KiB/s; a 4X drive, for instance, would write at around 600KiB/s.

There are mechanical limits on the maximum angular velocity at which discs can be spun: at 25000 RPM and beyond, the tensile stress on the disc can cause the polycarbonate to warp and shatter.

For this reason, more recent high-speed recorders tend to use the Z-CLV (zoned constant linear velocity) scheme. This divides the disc into stepped zones, each of which has its own constant linear velocity. A Z-CLV recorder rated at "52X", for example, would write at 20X on the innermost zone and progressively step up to 52X at the outer rim.

See also

External links

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