The purpose of this article is to provide an introduction to the measuring signals related to the evaluation of the quality of a Blu-Ray recorded disc. Of course, evaluating quality with the various drives and media we used was also a goal, but it should be left aside for now, since the technology is still trying to get a stable foothold on the market.

The discs we used in the test were burned at 2X and some at 4X. Regarding the recording process, it seems that both the 2X and 4x writing strategies are quite efficient. The measurements showed that the pit/land shape was adequate. In addition, the reflectivity, a basic parameter in optical media, is also very good and stable over the disc. On the other hand, we cannot neglect the fact that uncorrectable digital errors occurred with many discs. But these cannot be attributed solely to the writing process, since handling and its affects on the media plays a major role.

The Blu-Ray disc format uses a laser with a Numerical Aperture of 0.85nm. This means that the laser beam that accesses the data is very narrow, compared to CD and DVD. As a result, the laser beam can be easily diffracted by small particles or defects that exist on the disc's surface. The size of these particles could be microscopic, as in the case of the dust or smoke. In the picture below you can see how a particle interferes with the laser beam of a reader in the CD, DVD and Blu-Ray disc formats.

Our test measurements confirmed this. The cleanliness of the read side of the media seems to have a great impact on the disc quality. For example, there were cases where discs were measured and produced very high Uncorrectable errors. Of course, these discs were out of specifications and as a result, they should have been rejected. But after cleaning the discs with special air spray and appropriate tissues, we re-measured them (Pass 2), and UNC errors were dramatically reduced or even disappeared altogether.

Cleaning the disc surface of a disc before reading/testing was essential in the case of previous generations of optical media (CD and DVD) but as the pit/land structure is much smaller on high definition media, even particles of dust - not to mention fingerprints - make playback quite difficult, which correspond to extremely high peaks in digital errors during measurements.

Despite the existence of UNC errors, the DaTARIUS driveCube system did not lose track. In addition, the discs used in this test were readable with commercial Blu-Ray drives.

However, it would not be wise to make a clear statement on the playability of the Blu-Ray media of this test in a consumer environment. From a technical point of view, the discs we tested were in some cases out of specifications, but as seen with DVD video, digital errors do not always lead to video/audio distortion. We aim to do a more in depth study of high definition media by creating a batch of discs with video content and have the discs tested on a panel of consumer players available on the market.

For now, our first test with Blu-Ray media brought to the surface a serious parameter related to Blu-Ray discs: The necessity for very careful handling and storage.