Blu-Ray - Blue lasers
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The biggest difference between DVD and Blu-Ray is the color of the laser reading the disc. Colors are just visible wave lengths. Each color has a different frequency on which it is seen. Some colors have larger frequencies then others. Red has a frequency of 600-780 nm in size, while the blue has a frequency in the mid 400s nm.
The smaller the frequency, the smaller the gap can be between rings of data on a CD. The smaller the rings, the more rings you can have. On DVD players the laser is red. With Blu-Ray it will be a bluish violet, more violet then blue. This could make backwards compatibility a problem, but the manufacturers say that all their Blu-Ray drives will be backwards compatible. They should be able to read and write CDs and DVDs. Whether they will support dual layer DVD is still up in the air, and may very by model.
So now you have the picture that you can fit more data into a Blu-Ray than a DVD, but how much more? A standard DVD can hold 4.7 GB, with a dual layer holding twice that, 9.4 GB. Blu-Ray Discs with a single-layer can fit 23.3GB, 25GB or 27GB. For a dual-layer disc we double those to get 46.6GB, 50GB or 54GB. That’s ten times the space of current DVDs. Blu-Ray will not stop at dual layer like DVD; Blu-Ray manufacturers hope to fit multiple layers into a single disc, and we could easily see 100GB or even 200 GB before the end of the line for Blu-Ray.
The current writing speed is 1x. At that speed, it will take roughly one hour and 33 minutes to fully burn a 25 GB Blu-Ray disc. The 2x speed is currently under development, and should be out before Blu-Ray hits the mass market. Hopefully we will see 8x or higher in the coming years after Blu-Ray starts its take over of the market.
Next: Why not HD-DVD? >>
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