Blu-ray is a format for high definition DVD. More and more people are upgrading to – or have already upgraded their TV to a LCD or plasma TV which will most probably be capable of displaying the latest high definition (HD) pictures. High Definition TVs playing HD content display brighter colours, far crisper images and a sharper picture. Mostly the HD content will be HD digital content sent through an HD box such as a HD Sky box or a Blu-ray DVD Player or another type of device with a Blu-Ray disc inside.
Like a standard DVD or CD player and recorders the Blu-ray Player reads the data from the spinning reflective disc using a laser. How much such information can be stored on the disc depends on the wavelength of the laser light used to record or read the data. Ordinary DVD devices use a red laser which has a wavelength of 650 nanometres and a double-sided disc can store up to 8.5GB of data enough for a standard film. A HD film needs much more storage space than this and a Blu-ray disc with a much larger capacity is needed. Blu-ray devices use blue-violet lasers – a shorter wavelength of 405 nanometres where the shorter wavelength of the laser gives more precision to cut narrower tracks and store much more data. A single layer disc can hold 25GB of data and a double-sided disc 50GB. Future technology will be multi-layered discs increasing storage up to 200GB. Blu-ray players are also able to play ordinary DVDs though not with High Definition.