Thermo-Balanced Writing
If this initial test shows some discrepancies, then the algorithm goes to its main sequence. In one or more test
burn/read iterations the required burn pulse data is recalculated, and if necessary, the disc is reassigned to the
next lowest drive speed available.The calibration stops when the results show a correct performance within
defined tolerances. The disc is then recorded with the revised conditions.
What happens is a fast sequence of tests that determine precisely the power dosage of the laser burn pulses
that need to be applied to the particular disc that the TBW intelligent CD-RW drive itself discovers to have
been inserted in the disc tray.
After final testing, recording can begin and the burn process tailors the laser pulses to give exactly the right
amount of heat so as to create a sequence of signal pits all having the right size and density.The result is an
optimal ratio of reflectivity between pits and lands, with the correct size and spacing defined. Thus the drive
maintains a high degree of accuracy in writing, readability and above all, compatibility.
Note, as well as intelligently calculating the optimal burn parameters, the choice of disc speed is made
automatically without any intervention by the user. The user is always assured of a disc being recorded under
optimal conditions.
End-users may notice that recording takes place slower (or faster!) than expected (e.g. compared to the
information on the disc packaging) but they should almost never see a wasted disc resulting from a recording
failure due to this type of problem. As expected, end-users are informed via the application of the new selected
recording speed.
In other words, the TBW intelligent drive can calibrate itself and so automatically compensates for variables in
the recording media; and every disc is treated individually.This feedback system offers other advantages over
one with fixed parameters: if the laser characteristics vary over time or if it suffers from a build-up of dirt, the
effect on its output will automatically be compensated for by the TBW feature.This makes for greater reliability,
and longer useful life of the drive itself.
The advantage is real
Extensive development and testing of the TBW and Self Learning features was done in the Philips Research
Laboratory in the Netherlands, and Philips Development Centre in Belgium. The testing is ongoing, and covers
most CD-R media currently available on the market, and has demonstrated the real advantage of Philips
solution. Most sub-specification CD-R media can now be satisfactorily written and read with a very limited
chance of rejection.
In addition to satisfactory practical tests, objective evidence of the reality of the quality obtained by TBW can
be demonstrated (see Fig.3).TWB also forms the basis of a new proposed effort aimed at high speed
recordable media standards.
62200223-TBW 21-02-2001 16:15 Pagina 10
