Blu-ray Dimensions

TDK 25GB BD-RE Blank Disc in Jewelcase

Blu-ray Disc Rewritable recordable discs make it possible to back up large data directories, record HD video, and store large amounts of data, music and video all on one disc. Like other recordable discs BD-RE uses phase change recording technology to make it possible to erase and write again.  A special phase change metal alloy can be switched back and forth between a crystalline phase and an amorphous phase, changing the reflectivity, depending on the power of the laser beam.  Data can thus be written, erased and re-written.  Some companies claim on upwards of 10,000 rewrites per disc with little degradation. Rewritable recordable  Blu-ray discs use the same 405nm blue laser that write once read many (WORM) recordable Blu-ray discs use. Data capacity for BD-RE is currently 25GB or 50GB.

Currently TDK and MAM-A are the only manufacturers of rewritable Blu-ray discs.  TDK is much more common and the leader in production (currently).

There are several other manufacturers of BD media including Ritek and FTI.   TDK  does OEM work so there are many “brands” out there.  Rewritable Blu-ray discs are specialized and cost more then standard recordable Blu-ray disc media.  BD-RE discs provide far greater rewritability then CD-RW and DVD+RW that top out at one hundred rewrites.

Blu-ray rewritable recordable discs offer large capacity storage for data backups and HD recording and rewriting.

With the growing demand for high-definition video Blu-ray disc provides an excellent choice for the consumer.  Even better is the fact that a recordable Blu-ray format exists that allows for recording your favorite shows in high-definition. Both write-once and rewritable Blu-ray disc media exists in 25GB and dual layer 50GB capacity. Almost 5 times the storage of standard recordable DVDs.  Blu-ray recordable represents a huge jump in capacity that not only allows for less compression of the video signal but gives even more room for features that were just a dream in DVD format.

So what makes recordable Blu-ray so much better then DVD?

Blu-ray technology uses a violet-blue laser which operates at a higher frequency then the red laser that DVD relies on.  This allows for the information (or pits) to be placed closer together on the same sized disc as DVD.  This change of lasers requires additional lasers for backwards compatibility with DVD and CD.  Unlike the past format releases (DVD specifically) consumers do not have to face the decision of upgrading to a new format and casting aside their current library.  Blu-ray readers and recorders have been designed to provide full support for the older formats.

One of the little known facts of the new BD-R format is it’s construction vs. DVD recordable.  Blu-ray recordable discs use a single polycarbonate disc which provides better sealing against oxidation then recordable DVD.  Recordable DVD’s use two layers: a sandwich with the dye and reflective layer in the middle.  The only thing keeping the DVD recordable disc from separating is glue. As production of DVD recordable has been perfected the separation of the two parts is less likely but still a concern. Not only from the outside of the disc but the hub in the center where it is in contact with a locking mechanism when stored in a DVD case.  As this glue fails it allows oxygen to enter the disc at a faster rate then through the plastic itself.  Oddly enough recordable CD-R have a far longer archival life then recordable DVD.  This is because CD-R (like Blu-ray recordable) has a single layer of polycarbonate with various sealing layers on top that provide greater reduction of oxidation then the DVD sandwich.

So besides the increase in storage capacity Blu-ray also offers greater longevity then recordable DVD media.  How much longer is being tested right now by most of the blank blu-ray disc media manufacturers.