In 1997, a new technology emerged that would signal the end of the humble VHS cassette and bring digital sound and video to people all over the world. Yep you guessed it, I’m talking about the DVD, and since its arrival the DVD has revolutionised the movie industry, and we all now wondered how we ever put with the VHS Cassette
Well the ever evolving world of technology is set to revolutionise our movie watching experience even more with the relatively new Blu-Ray disk. Blu-Ray Disks have been around since 2006, but as with all new technology that is newly released on the market the price and peoples general scepticism kept it from being hugely popular.
The name Blu-ray is derived from the underlying technology, which utilizes a blue-violet laser to read and write data. The name is a combination of "Blue" (blue-violet laser) and "Ray" (optical ray). The Disks have a high storage capacity which is needed to hold and play back high definition video and other digital content.
A current, single-sided, standard DVD can hold a maximum of 4.7 GB of information. That's about the size of an average two-hour, standard-definition movie with some extra features. But a high-definition movie, which has a much clearer image and clearer sound quality, takes up about five times more bandwidth and therefore requires a disc with about five times more storage. As TV Sets and movie studios make the move to high definition, consumers are going to need playback systems with a lot more storage capacity.
A single-layer Blu-Ray disc which is around the same size as the DVD, can hold up to 27GB of data. A double-Layer Blu-Ray disk can store up to 50GB of data. There are also plans to make a disk which will be able to hold twice that amount of storage.
Building a Blu-ray Disc
So we’ve established that Blu-ray discs have more storage capacity than traditional DVDs, but that’s not all! They also offer a new level of interactivity. Users will be able to instantly download subtitles and other interactive movie features via the internet, record high definition television without any loss of picture quality or sound, record one programme while watching another on the disk, and instantly skip to any spot on the disk.
Discs store digitally encoded video and audio information in pits, which are spiral grooves that run from the centre of the disc to its edges. A Laser reads the other side of these pits known as bumps, to play the movie or program that is stored on the DVD. The more data that is contained on a disc, the smaller and more closely packed the pits need to be. The smaller the pits (and therefore the bumps), the more precise the reading laser has to be.
Current DVDs use a red laser to read and write data, Blu-ray uses a blue laser. A blue laser has a shorter wavelength (405 nanometers) than a red laser (650 nanometers). The blue laser beam focuses more precisely, enabling it to read information recorded in pits that are only 0.15 microns (µm) (1 micron = 10-6 meters) long, this is more than twice as small as the pits on a DVD. Blu-ray has also reduced the track pitch from 0.74 microns to 0.32 microns.
Blu-ray disc are about the same thickness as a DVD. But the two types of discs store data differently. A DVD has data sandwiched between two polycarbonate layers, each of which are about 0.6mm thick. Having a polycarbonate layer on top of the data can cause a problem called birefringence. This means the substrate layer refracts the laser light into two separate beams. If the beam is split too widely, the disc cannot be read. Additionally, if the DVD surface is not completely flat, and so not exactly perpendicular to the beam, it can lead to a problem known as disc tilt, in which the laser beam is distorted. All of these issues lead to a very complicated manufacturing process.
The Blu-ray disc manages to overcome DVD-reading issues by having the data on top of a 1.1mm thick polycarbonate layer. Having the data on top prevents birefringence and so prevents readability problems. With the recording layer sitting closer to the objective lens of the reading mechanism, the problem of disc tilt is virtually eliminated. Because the data is closer to the surface, a hard coating is placed on the outside of the disc to protect it from scratches and fingerprints.
Blu-Ray disk, unlike standard disks come equipped with a secure encryption system which protects against video piracy and copyright infringement.
The way the Blu-Ray disk is designed also saves on manufacturing costs. The standard DVDs are built by injection molding the two 0.6-mm discs between which the recording layer is sandwiched. The process must be done very carefully to prevent birefringence.
Blu-ray discs only do the injection-molding process on a single 1.1mm disc, which reduces cost. That savings balances out the cost of adding the protective layer, so the end price is no more than the price of a regular DVD.
So I think you will agree that Blu-Ray technology really is amazing. Of course if you want to take advantage of this technology you will need other technology that works in conjunction with the Blu-Ray technology. You will need a Blu-Ray player because as we already know the new Blu-Ray disks are read in a different way to standard DVD’s and so won’t play in a standard DVD player. Also, to get the full benefit of the sound a viewing technology a Hi-definition TV will definitely be required.
