History of Blu-Ray Discs

Blu-ray discs are a type of optical storage media that has been designed to supersede the DVDs. It offers huge storage capacity, about 10 times the storage capacity of DVD. There are two types of blu-ray discs – single layer that can store up to 25 GB of data and dual layer that can store 50 GB of data. These discs are mainly used for storing high definition movies and Sony Playstation 3 games. The physical appearance and the dimensions are same as any standard DVD. The name blu-ray comes from the laser light which is blue-violet in color used for reading and writing purposes. Blu-ray discs can store more data due to the fact that the laser light of shorter wavelength is utilized to read and write on to the disc. It uses 405 nm blue-violet laser light. The shorter wavelength can be focused properly and occupies lesser space compared to 650 nm red colored laser light used by DVD media.

When blu-ray discs hit the market, there was tough competition from HD DVD (which is also termed format war). Toshiba was behind the promotion of HD DVDs and tried its best to make HD DVD popular. There are many drawbacks associated with HD DVDs and Toshiba had to back down. The format war came to an end in early 2008 and Toshiba started making its own blu-ray devices. Blu-ray discs superseded the HD DVDs. The blue-ray discs is developed by the blu-ray disc association which is a group comprising of computer hardware, consumer electronics and motion picture associations. In matter of just an year, thousands of movies and games were made available on blu-ray media. There were many issues for commercialization of blu-ray technology and devices. Initially, the devices were very expensive and the blue laser diode invented by the Shuji Nakamura could not be utilized because of lawsuit.

Blu-ray discs were based on optical rewritable discs which used ultra density optical diodes and DVR blue. The DVR prototypes that were developed came to known as blu-ray discs. Blu-ray discs were commercially available in the year 2003 and were only available in Japan. The blu-ray device – Sony BDZ S77 was very expensive and priced at $4000.No movies were released for the player and had no standards. The physical specifications and other standards came in to existence in 2004. Sony, Toshiba, Samsung and Pioneer were the companies that started producing blu-ray discs. The BD ROM players were actually introduced in the year 2006 and had to face competition from HD DVD ROM players since they arrived in the market 6 months earlier. Mpeg 2 codec were used, later AVC and VC1 were also implemented. 50 GB dual layer discs were commercialized in 2006. The first writer that became famous was blu-ray disc rewritable drive – BWU-100 A from Sony. The writer supported both single and dual layer discs and also BD RE discs. Blu-ray became extremely popular after the format war ended and was better accepted than DVD format. 9.6 million blu-ray devices were sold in 2008.

Blu ray discs uses Indium Gallium Nitride lasers that produce 405 nm photons without using any mechanisms like non-linear optical mechanisms or frequency doubling. The regular DVDs and CDs use red infrared lasers at 650 and 780 nm respectively.

The shorter wavelength makes it possible to focus laser light on a smaller spot size that boosts the size of the optical media. The spot size of the blu-ray disc may be equivalent to 580 nm. Data encoding techniques have also been improved that has contributed to the success of the blu-ray discs. Although the blu-ray discs out beat the DVD discs in every manner, the blu-ray discs are more prone to damage or scratching of the disc since the data layer is very close to the disc surface. Cartridges were being used, but it made blu-ray discs even more expensive. Later scratch protection coatings were developed and it was first introduced by TDK. Nowadays, many companies have their own customized hard coat technology to protect the data layer of the blu-ray discs. Blu-ray discs have come a long way and they are the next generation storage media. Many companies are trying to produce even higher storage capacity discs that can store over 100 GB.

The advantage of blu-ray disc over the DVD is that the data is placed directly on the top of a 1.1 mm thick polycarbonate layer. This avoids all the readability issues, since birefringence (double refraction) is prevented. Birefrigence is a phenomenon in which light waves are split into unequal transmitted or reflected waves through an optically anisotropic medium. The disc tilting problem present in the DVDs is completely avoided, since the data layer is situated closer to the object lens. This closeness may cause damage to the data layer and hence the layer is coated with hard coat to avoid finger print and scratches.

The design of blu-ray discs is such that it avoids manufacturing costs. DVDs are built using injection molding process, which uses two 0.6 mm discs and the recording layer is sandwiched between them. The process has to be carried out extremely carefully to avoid birefringence. After molding, the recording layer is attached to one of the discs and the two discs are glued together. In the case of the blu-ray disc, the injection molding process is carried out on a single 1.1 mm thick disc. This saves the manufacturing cost and the savings is used for protecting the layer. The data transfer rate of a blu-ray disc is 36 Mbps that is 3.5 times more than a latest DVD – 10 Mbps. Future for blu-ray discs and devices look very bright.