Blu-rayBlu-ray disc is the next generation optical disc format meant for high definition video (HD) and high density data storage, and is one of two competing standards for HD optical media. Its competitor is HD-DVD. Blu-ray gets its name from the shorter wavelength (405 nm) blue (technically blue-violet) laser that, in addition to other techniques, allows it to store substantially more data on the same sized disc than DVD, which uses a longer wavelength (650 nm) red laser. Blu-ray has information capacity of 25 gigabytes per layer. Four-layer 100 GB disc is coming soon. Data on disc is so closed that a clear polymer coating is necessary to protect it from scratches and dust (without using plastic caddies).