Thermo-BalancedWriting
Thermo-BalancedWriting
Therm o Balanced W riting
fo r o p t im a l r e c o r d in g
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Thermo-BalancedWriting
temperature
Fig.1,Thermo-
BalancedWriting:
laser beam
Typical Heat Profile
during CD-R write
phase.Goal ofTBW is
to ensure a correctly
balanced heat profile
during this phase.
required temperature to
burn a pit
diameter of pit is smaller
than diameter of laser spot
laser spot
Equally of course,if the pits come out too small or too light,then other reading errors can occur.If a CD-R
drive has no way of controlling the burn process,to adapt itself to the nature of the media,then the use of such
sub-standard discs is far more likely to result in defective recordings and,more importantly,severe End-user
disappointment.
Fig.2,Thermo-
BalancedWriting:
Pit & Land Cross
section. A build
up ofThermal
“cross-talk”during
successive “burns”
creates pits
with variable
dimensions,and
the possibility of
errors when data is
read back.
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Thermo-BalancedWriting
Unfortunately,there is no reliable way a consumer can judge what he or she is buying (as example,an
authoritative quality logo on the disc packaging or verification of media confirmance),and so when an End user
buys and "burns" what are,in effect,sub-standard discs,any resulting problems are liable to be attributed more
often to the CD drive unit then to the disc.It is a question of compatibility,something the End user implicitly
desires,and unfortunately,is not able to recognise whether it is there or not.
The solution
Philips,anticipating End user concerns about disc compatibility and data integrity,has applied considerable
effort to developing and testing a system of self-calibration for recording CD-R discs. This solution is "on
board" in the drive itself,and provides an excellent solution. It is part of a continuous Philips programme
devoted to the perfection of CD technology,and particularly,to anticipating and solving End user problems,
thus enabling greater Ease of Use.
The Philips solution lies in a technique designatedTBW [Thermo-BalancedWriting],a feature which is to be
introduced in all new Philips CD-RW drives.TBW,partnering with a Self-Learning process,adds intelligence to
the drive and enables it to automatically make decisions about how to process and write a new disc.
CD-RW drives also write CD-RW discs of course,however,TBW technology is not applicable to the RW
function as CD-RW discs utilise a completely different recording methodology.
TBW allows many discs of lower quality to be used without anxiety,and with the assurance that the drive will
automatically determine the integrity of the recording layer,then automatically select the correct burn
conditions and associate these always with the optimal appropriate recording speed to ensure compatibility.
The process is similar to the way in which modern fax machines communicate to detect what kind of partner
machine is at the other end of a connection so that the two can transfer data properly without the user having
to guess what might be there and press buttons to set up the link.
The heart of the Philips solution is a new hardware and firmware built into the drive with theTBW algorithm
which evaluates the disc and determines the burn parameters.
The intelligent algorithm
When a disc is inserted in the drive with intention to write,the start logic immediately triggers the partner to
TBW,the self learning algorithm.In a brief interval of time,unnoticed by the End user,a sequence of physical
tests are performed on the disc to determine its’ characteristics.
On insertion,a test is automatically made in which a series of test pits are burned into the disc at the
appropriate speed and with the burn laser pulsed as necessary to achieve the optimal relationship between pits
and lands,in particular,to provide the correct reflectivity differential,the correct position,length and spacing of
each element and an acceptable block error rate.The test burn is then read and if the result corresponds,
within the tolerances allowed,then the disc is passed for recording under those conditions.
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Thermo-BalancedWriting
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 theTBW 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,theTBW 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 theTBW feature.This makes for greater reliability,
and longer useful life of the drive itself.
The advantage is real
Extensive development and testing of theTBW 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 byTBW can
be demonstrated (see Fig.3).TWB also forms the basis of a new proposed effort aimed at high speed
recordable media standards.
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Thermo-BalancedWriting
Fig.3 (Fig.3a & 3b),
Thermo- BalancedWriting:
Thermal“cross-talk”is
reduced byTBW.
fig 3a: Without TBW
fig 3b: WithTBW
Pit
Pit
The standard for Pit and Land length is represented by an intersection of the horizontal and vertical lines. The plots,
representing the individual measurements of each Pit and Land, in ideal circumstances (no“cross-talk”as example),
should be located on the intersections themselves.
The black“dots”in the illustrations represent the average of the measurements of Pit and Land length,and optimal
writing would place the black dot on or very near each intersection.
The two charts,one withoutTBW writing,and one with,clearly demonstrate an improvement in writing accuracy with
TBW technology especially at the 3T up to 5T pit combinations.(The 3T up to 5T pit combinations are used for approx.
70% of instances of writing data to disc).
The new Philips 12x8x32x CD-RW is the first product to have been introduced utilisingTBW technology and
from now,all Philips 8x4x32x CD-RW drives have this feature.
To sum m arise
TBW intelligent drive technology,developed and patented by Philips,is a powerful new feature that adds
significant End user benefit. End user confidence in recording CD-R discs is assured by a state-of-the-art drive
that can create recordings on previously questionable discs.Data integrity is assured by physically testing each
disc and then tuning the output of the recording laser and choosing the recording speed to suit each individual
disc. Even if the drive determines to use a recording speed lower than the maximum possible,it will always
choose the maximum speed which can safely be used for the disc inserted. New discs are likewise
characterised and then written to in accordance with their measured characteristics.
These methods result in an "intelligent" drive,which adapts its behaviour to suit the precise requirements of
each individual disc,ensuring the best possible recording quality on all media.It provides a very high success
rate even when recording on discs of a quality below the internationally recognised standards.
TheTBW technology is developed,qualified and already in production.
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Thermo-BalancedWriting
Philips O ptical Storage
Building SFH3
P.O.Box 80002
5600 JB Eindhoven
The Netherlands
© 2001 Royal Philips Electronics N.V.
All rights reserved.Specifications are subject to
change without prior notice.Reproduction in whole
or part is prohibited without written consent of the
copywright owner.
3104 145 550 901
Printed inThe Netherlands 2/01
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