Blu-Ray - Building the Disc

So you finally got all the right media for your DVD burner to burn those home videos to DVD to view on your TV. You pop the disc into your DVD player, and it doesn’t read. You are sure that it is the right format, so while you scratch your head I will tell you why this happened. It all has to do with how a DVD is made.

The manufacturers take two .06mm polycarbonate discs, and between them they sandwich the recordable layer. When the disc is read, the laser has to pass through one of the layers of polycarbonate, and it splits the beam into two parts; it's a lot like a prism. If the two parts are too far apart, the disc will have trouble being read. This is called birefringence.

Blu-Ray discs will be built slightly differently, to prevent birefringence. The disc will be built upon a 1.1mm thick polycarbonate layer. There is only one layer; the data layer sits on top of that. There is no other layer to interfere with reading the disc. The down side is that the disc could be easily scratched, so makers of Blu-Ray discs will add a hard coat to protect the data from scratches. TDK is one of the leaders in scratch proofing Blu-Ray. They are producing discs that can be ground with sandpaper and still be fine.

There will be a few different types of Blu-Ray discs. The BR-ROM is for commercial uses such as games and movies. You can read them, but can’t burn anything new onto them. For consumers there will recordable (BR-R) and rerecordable versions for PCs (BR-RW). Unlike current DVDs there will be different rerecordable discs for HDTV recordings, called BD-RE.

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