This is what enables the Blu-Ray disc to store so much more information. Blu-ray discs are also more scratch-resistant than DVDs. So, is it time to throw out all your DVDs and replace them? Maybe not quite yet. You also may not be able to find the movie you want yet in a Blu-Ray format. Please stop by our store at W. Greenfield Avenue to complete your collection. The more data that is contained on a disc, the smaller and more closely packed the pits must be.
The smaller the pits and therefore the bumps , the more precise the reading laser must be. Unlike current DVDs, which use a red laser to read and write data, Blu-ray uses a blue laser. A blue laser has a shorter wavelength nanometers than a red laser nanometers. The smaller beam focuses more precisely, enabling it to read information recorded in pits that are only 0. Plus, Blu-ray has reduced the track pitch from 0.
The smaller pits, smaller beam and shorter track pitch together enable a single-layer Blu-ray disc to hold more than 25 GB of information — about five times the amount of information that can be stored on a DVD. Each Blu-ray disc is about the same thickness 1. But the two types of discs store data differently. In a DVD, the data is sandwiched between two polycarbonate layers, each 0.
Having a polycarbonate layer on top of the data can cause a problem called birefringence, in which the substrate layer refracts the laser light into two separate beams. If the beam is split too widely, the disc cannot be read. Also, if the DVD surface is not exactly flat, and is therefore 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 involved manufacturing process. Having the data on top prevents birefringence and therefore prevents readability problems. But the two types of discs store data differently. In a DVD, the data is sandwiched between two polycarbonate layers, each 0. Having a polycarbonate layer on top of the data can cause a problem called birefringence , in which the substrate layer refracts the laser light into two separate beams.
If the beam is split too widely, the disc cannot be read. Also, if the DVD surface is not exactly flat, and is therefore 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 involved manufacturing process. The Blu-ray name is a combination of "blue," for the color of the laser that is used, and "ray," for optical ray.
The "e" in "blue" was purposefully left off, according to the manufacturers, because an everyday word cannot be trademarked. The Blu-ray disc overcomes DVD-reading issues by placing the data on top of a 1. Having the data on top prevents birefringence and therefore prevents readability problems. And, 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. The design of the Blu-ray discs saves on manufacturing costs. Traditional DVDs are built by injection molding the two 0. The process must be done very carefully to prevent birefringence. Blu-ray discs only do the injection-molding process on a single 1. 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.
Blu-ray also has a higher data transfer rate -- 36 Mbps megabits per second -- than today's DVDs, which transfer at 10 Mbps. A Blu-ray disc can record 25 GB of material in just over an hour and a half. Blu-ray discs are better armed than current DVDs. They come equipped with a secure encryption system -- a unique ID that protects against video piracy and copyright infringement.
Unlike DVDs and CDs , which started with read-only formats and only later added recordable and re-writable formats, Blu-ray is initially designed in several different formats:. Will Blu-ray replace previous DVDs? Its manufacturers hope so. But Blu-ray is not alone in the marketplace.
A few other formats are competing for a share of the DVD market. The advantage to HD-DVD is that it uses the same basic format as the traditional DVD and can therefore be manufactured with the same equipment , saving on costs. The read-only versions hold slightly less data. Blu-ray and HD-DVD are the two major competitors in the market, but there are other contenders, as well. Warner Bros. This system uses a higher compression rate to put more information about two hours of high-definition video on a standard DVD.
There are also professional versions of the blue laser technology.
0コメント