Blu - ray

Blu-Ray is a new generation optical disc used to store high definition video and heavy data.

It looks just like a regular CD or DVD as it has the same shape and diameter (12 cm) in which information is codified, kept and stored by making microscopic grooves with a blue laser in one of its sides.

Also the same file extensions can be recorded and read from it.

Its capacity is larger than the capacity of a DVD because the wavelength of a blu-ray is much shorter (405 nm as opposed to 650 nm).

In a blu-ray you can store up to 25 GB per layer and most of them have two layers, but 16 layered discs have already been patented and in 2011 it is expected to increase up to 1 terabyte.

Blu-ray got its name from the blue laser it requires, but the 'e' from the word 'blue' was left behind because in some countries common words cannot be registered for commercial names.

Blu-ray appeared to substitute DVDs (which were on their way to substituting CDs), and it defeated its competitor: HD DVD. It was developed by an association of companies leaded by Sony and Philips.

Nowadays the capacity, resolution and quality of DVDs has been exceeded: from 720x576 to 1920x1080.

This last format is the one used by the movie industry to store their production and before it was necessary to convert it into a different format in order to export it. However, now it can be exported as it is, and this saves effort, time and mainly costs.

There were two main problems that surrounded DVDs that blu-ray technology has tried to solve, and so that, although appearance is the same, the structure is different.

To begin with, in order to read DVD, the laser has to go through a thick layer of polycarbonate. This makes diffraction (ray division) a big problem, because if there is any dirt or scratch on the surface, the disc cannot be read.

In blu-ray this layer is much thinner and this problem is reduced proportionally to the reduction of the distance between the laser and the disc (it is now six times smaller, from 0.6 mm to 0.1mm).

Also, this layer is much more “scratch-resistant”.

Secondly, if a DVD disc was not horizontal or the laser did not incise perpendicularly, the distortion would again bring trouble when it came to reading.
Thanks to the small distance between the laser and the surface this problem is again solved in most of the cases and errors can be avoided.

Another important characteristic of blu-ray is that, as a consequence of the small distance separating the disc and the laser and the thinness of the layer we have mentioned before, it is very prone to being accidentally scratched or get dirty.

In order to find a solution, the first thought was to commercialize it inside some kind of casing, but this idea was rejected thanks to the development of a protecting substrate, called “Durabis”.