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Measure - Calibration

All DaTARIUS CD and DVD measuring systems can accommodate any range of calibration complexity that the user desires. The chart below shows ‘Calibration Population Range’ versus ‘Calibration Sophistication’.

‘Calibration Population Range’ is a rough indicator of how many different ‘types’ of disc can be accurately measured with the chosen calibration technique. The ‘type’ of disc is a disc of a given manufacturing process. For example, if a single calibration disc is used, then the discs for which the calibration will be most accurate will be those discs that are physically and optically most similar to the calibration disc, based on the manufacturing process parameters. In other words, the measuring systems will be most accurately calibrated for discs that were made with thickness, mould temperature, cycle time, stamper pit geometry, etc, that are similar to those of the calibration disc.

Calibration Sophistication’ is a rough indicator of how complicated the calibration procedure is for the chosen calibration technique. The extent of Calibration Sophistication is continuous, and can range from very simple to very complex. It is divided into the three areas Simple, Normal, and Advanced for discussion purposes only.

Simple Calibration would involve using one or two discs to calibrate the measurement system, using one or two calibration reference points per parameter calibrated. For example, using a Philips 5B3 for CD, or the Philips Signal Discs, or similar discs, for DVD, and using the same discs that are used for calibration to check the calibration.

The main advantages of Simple Calibration are that is it easy and quick. The reference files are very short and simple, and are available from DaTARIUS. A complete calibration for DVD can take as little as 15 minutes, and CD is even quicker.

There are two main disadvantages of Simple Calibration. First, the Calibration Population Range is small, and is limited to discs that are close in process to the calibration discs. In the example mentioned for CD, the Philips 5B3 disc was manufactured with a 9-second cycle time, giving very flat-bottomed 3T pits. There are virtually no currently produced CDs that are manufactured in this way. Second, the fact that the same discs that are used to perform the calibration are also used to perform the check means that the calibration never fails. In other words, there really is no check to the calibration accuracy since, unless something is very wrong with the system, the check values will always read correctly at the calibration points, though they may be off on other discs.

Normal Calibration uses discs that are closer to production discs, and more of them. These can be, for example, the DaTARIUS Calibration Discs that are supplied with the measurement systems.

Normal Calibration is more complex than Simple Calibration, in order to increase the Calibration Population Range. This calibration takes longer to perform, because more reference points are measured to maximize the calibration accuracy over a wider range of disc types. Also, the calibration checkpoints are not the same as the calibration points, so the calibration check performs a real evaluation of the quality of the calibration. The calibration reference file is also more complicated, but this reference file is provided by DaTARIUS in the case of the DaTARIUS calibration disc sets.

Advanced Calibration, as the name implies, is for advanced users, or actually any users - with the help of the experts at DaTARIUS Customer Service! As the chart shows, users can create reference files, or modify existing reference files, to either decrease or increase the Calibration Population Range, or for any other special purposes that they may have.

An example of why users would want to decrease the population range would be to ‘fine-tune’ their measuring systems for their processes. In other words, in a situation in which users have a well-defined process window, they can use calibration discs that they have manufactured themselves to make sure that the measuring systems are very accurate over the entire range of discs that they produce, though that accuracy would fall off if they measure discs from a different manufacturer.

An example of why users would want to increase the population range would be the case in which they receive stampers from several different external sources for replication. In this case, users would want to create a calibration disc set to represent the range of discs they make, based on the various stampers they use, to maximize their calibration accuracy across this wide range of discs.

An example of a special purpose would be the case in which the user has occasional deliveries to a customer who uses one particular measurement system for incoming inspection. In this case, users can create a calibration reference file such that their measurements match the measurements made at this particular customer site. Regular calibration would then be used for most of the production, and be switched to the special calibration with jobs for this particular customer.

As can be seen, Measurement Systems from DaTARIUS have all the flexibility necessary to create whatever type of calibration that the customer desires. Use either a simple or normal calibration with no effort, or customize the calibration regimen in nearly infinite combinations. Calibration may be made as quickly and as easily as needed. Alternatively create a calibration routine that, while it may take longer to complete, covers the exact range of discs that need to be tested with superb accuracy.



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