Development Of Blu-ray DVD Format

Blu-ray disk format was created for playing back and storing of HD-video but it is also ideal for other applications as well like personal computer data storage, video game consoles and similar other consumer electronic equipments. The wavelength of the blue laser is 405nm. High definition DVD is capable of recording maximum of 15GB and the blu-ray can record 25GB data on one single layer disc. Sony carried out experiments with different extreme values and tried the 400nm (shortest wavelength) and numerical aperture’s highest value. An optical lens’s numerical aperture is the capability of lens to focus the laser light at specific distance and point. As the numerical aperture goes higher, the distance becomes lesser. Optical disk’s capacity of recording data is dependent on the spot size of the laser beam. This spot size is proportional to the wavelength of the laser beam. Therefore the capacity of holding data will be inversely proportional to objective lens’s numerical aperture (NA). Increase in NA and decrease of laser beam’s wavelength helped to increase the data recording ability.

Sony decreased the wavelength of used in digital versatile disks (650nm) to 405nm and also increased the NA to 0.85 from its previous 0.60 which helped to enhance the recording capacity 2.5 times more. That is how the Sony Blu-ray became capable of storing 25GB. High definition DVD having the same physical recording space can only store data of 15GB and DVD can hold data of 4.7GB.   DVD was 0.6mm disk with protective coating of 0.6mm. Sony modified the structure of the disk and developed disk (1.1mm) with protective layer of 0.1mm.

The thickness of internal layers of HD-DVD and the blu-ray disk is different but their thickness is same of 1.2mm. So this makes the blu-ray format more capable of recording huge amount of data and of course more data than the High definition DVDs. In blu-ray disk the material for reading is thinner because the layer of data is nearer to the disk surface when compared to data layer of HD-DVD & DVD. Thinner protective layer enables reduced pitch of tracks among the smaller pits, higher numerical aperture’s value and increased data density. Blu-ray disk required initially a bulky cartridge for the protection of disk as the data layer was very near to surface of the blu-ray disc. That is how the Sony Blu-ray became capable of storing 25GB.

TDK is also a member of BD association. TDK afterwards introduced “DURABIX” which was useful and advantageous coating technology that enhanced blu-ray media’s resilience and so DURABIX abolished the requirement of cartridges for recording layer’s protection. The variation in the structure of the blu-ray disk makes it different from DVD and the HD-DVDs. Sony offers solution whose speed and recording capacity both are higher than the other technologies of disk format.  

Blu-ray disk content is protected by the same technology used in the HD-DVD format. This technology for content protection was introduced by technology group Advanced Access Content System (AACS) licensing administration. The founders of this technology group were Intel Corporation, Panasonic, Toshiba, IBM, Warner Bros. Studios, Walt Disney, Sony and Microsoft. The AACS technology group is specification for the management of stored content on optical disk format’s next generation like blu-ray and High Definition DVD.

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