Thermo-Balanced Writing
A new, patented, system addressing the problem of writing reliably to the very many brands of
recordable CD media now on the market, not all of which are in conformance with the agreed
international standards established for use in Philips CD-RW drives.
Introduction
The explosion in demand for CD Recordable (CD-R) discs and the relentless pursuit of ever lower costs and
higher speeds has led to the production and sale of a great many makes and types of discs, both branded and
unbranded. Numerous manufacturers all over the world are now producing what has become a commodity
item. Unfortunately, in some cases, the quality of these discs are not in accordance with global standards set out
in the Orange Book for CD-R media.
The original intent underlying the development and marketing of the expanding family of Compact Disc audio
and data drives and their various media types and applications was to have the maximum degree of
compatibility, including backwards compatibility, wherever possible. For this reason, the series of agreed global
or international standards comprised in the Orange Book have been developed in co-operation and agreement
of all major firms involved in the development and exploitation of this technology.
It is this common standard and the insistence on compatibility, which has largely been responsible for the rapid
acceptance and intensive development and growth of this versatile storage medium.
Unfortunately, some CD-R discs available in the market do not match up in the basic technical parameters of
the standards established in the Orange Book. Production facilities and quality control may be inadequate, and
infrequently, sub-standard materials are used or dye layers are insufficiently and uniformly deposited on the
substrate.There can be patches of the disc surface almost without recording medium (in addition to scratches,
dirty marks or other surface defects), or gross mechanical damage which results in imbalance.
The CD-R process
The recording process used for CD-R discs relies on the heating effect of a laser pulse focussed on the dye
layer of the disc.Where the laser pulse is applied, a "pit" is created and the reflectivity of the surface is reduced.
The signal representing the (digital) data is recorded in the succession of these pits, separated by reflective
"lands" of unburned material.The current recording system (drive + disc) is very sensitive to variations outside
the Orange Book specifications, particularly when writing at high speeds (12x and higher).
For example, the heat produced by the laser pulse should be just enough to burn a pit to the right size and
density. However, if the dye layer is of poor quality, or the disc manufacture is otherwise defective (as an
example, unequal deposition of material), the right amount of cooling may not occur in the medium between
successive pulses.This results in dimensions of individual pits which can be too large and the possibility of
errors may occur in reading ( "cross-talk" between tracks).
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