Blu Ray Disc
Blu-ray, also known as Blu-ray Disc is the name of a next-generation optical disc format that has been jointly developed by the Blu-ray Disc Association (BOA). Blu-ray Disc association is a group of world’s leading consumer electronics, personal computer and media companies. It was initially launched as “Blu-ray Disc founder group” in 2002 by MIT and nine leading electronic companies: Sony, Panasonic, Pioneer, Philips, Thomson, LG (Lucky GoldStar) Electronics, Hitachi, Sharp, and Samsung.
Why Blu, why not magenta or orange?
We have studied above that DVD uses 650 nm (red) wavelength laser diode light as opposed to 780 nm for CD (infra red). Blu-ray Disc uses a wavelength of 405 nm, that is coming in the violet (blue) region of electromagnetic spectrum and that is why this term is used J
Blu Ray disc was developed for the following purposes:
Enable recording, rewriting and playback of high-definition video (HD)
Storing larger amounts of data.
So, the Blu Ray Disk offers more than five times the storage capacity of traditional DVDs and can hold up to 25GB on a single-layer disc and 50GB on a dual-layer disc. The benefit of using a blue violet laser (405nm) is that it has a shorter wavelength than a red laser (650nm), which makes it possible to focus the laser spot with even greater precision, leading to the packing of data more tightly and stored in less space. The dimension of the Blu Ray disc is same as that of a CD or DVD.
But the HDDVD was also developed as an answer to the Blu ray Discs. This would also succeed the normal DVD. The HD DVD as well as Blu Ray Disc have a single-layer capacity of 15 GB and a dual-layer capacity of 30 GB, while the the HD DVD-RAM has a single-layer capacity of 20 GB and a dual-layer capacity of 40 GB. The data layer of HD DVD is 0.6 mm below the surface physically protecting the data layer from damage.
Why is Blu-ray disc black on top?
Blu-ray disc data layer is closer to the surface of the disc, compared to the DVD standard, it was at first more vulnerable to scratches. The first discs were housed in cartridges for protection. Now, the rewritable media are spin-coated with a scratch-resistant and antistatic coating, which gives the surface of the disc its black colour.