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World of Blu-ray Drive > Blu-ray technology descriptionsiWhat kind of technology is Blu-ray?j

Rushing wave of digitization
High-definition programs viewed and recorded on personal computers
Blu-ray plays a principal role in the video lifestyle
So get started with Blu-ray right now
What kind of technology is Blu-ray?
Stable and secure with large data capacity
Structure and types of Blu-ray discs
Methods for using a Blu-ray Drive
Technologies of Pioneer

Blu-ray is the latest large capacity media technology. It is a global standard, featuring a disc the same size as a DVD but accommodating over five times as much data. Laser beams with a bluish violet color generated by a semiconductor are transmitted through a lens to create a thin flux of light, much like gathering sunlight using a magnifying glass. This thin light is rotated on a disc spinning at a high speed and measurements are taken on the portions that reflect and the portions that do not reflect. The processing of the difference between the two as digital data makes recording and replaying possible. Since there are no substantial changes in terms of the basic mechanisms from DVD or the like, the standard is highly stable with ample technologies already available from the starting phase.

With Blu-ray a lot more information can be recorded on an optical disc with a 12cm diameter, the same size as DVDs or CDs. This means that inevitably each individual piece of information must be made physically smaller.

In other words, this is a standard that involves concentrating the flux of light, made from laser beams, accurately onto narrow segments on the disc. This technology resembling a slim ballpoint pen is Blu-ray.


Imagine situations when it is necessary to fit in as many characters as possible on a piece of paper. A felt-tip pen that only allows the user to write bold letters may have been in use in the past, but replacing it with a ballpoint pen to write thin letters would make it possible to write many more characters on the same sheet of paper. Blu-ray is like this "ballpoint pen made to write thin letters".

The color of the laser beam used with Blu-ray is a bluish violet, in contrast with the red laser beam used with CD and DVD. This is the root of the naming, "blue" and "ray". The very important aspect here is the "wavelength of light". The wavelength of a red laser beam is 650nm (nanometers; one nanometer is one-one hundred millionth of a meter), the characteristic of the bluish violet laser beam of Blu-ray is that the wavelength is 405nm, which is substantially shorter.

For this reason it is possible to concentrate the light flux onto a smaller beam spot diameter when the laser beams are focused on the recording surface of the disc. This surface area is about one-fifth in comparison with a DVD. The distance between "tracks" (track pitch) on the disc, in which data is arranged in a line, as well as the minimum interval between the data within a track (minimum mark length), have been reduced significantly in comparison with a DVD. This is the reason why a large capacity recording is possible with Blu-ray.

Recording high-definition programs from terrestrial digital broadcasts

In the case of the "BD-ROM", which is a read-only medium, data is recorded within the layer provided within the Blu-ray Disc (BD). Spiral shape "tracks", originating at the inner diameter and running towards the outer diameter of the BD-ROM, contain a series of "bumps".

The reflection coefficient differs for the protruded and concaved sections. Laser beams are aimed at and traced along such tracks from the "pickup" to detect the differences in the reflection coefficient, which is read as digital data by interpreting it as "1 or 0". This is the mechanism involved in reading the data off a disc.

The technology known as "phase change" is used to write data onto a BD. Phase change is a "phenomenon, when the state of a particular substance is changed, although its structure does not change". The most familiar example of a phase change would be water changing into ice when cooled and ice changing into water when warmed. A laser beam is aimed at a special alloy layer provided inside the rewritable "BD-RE" to "change the reflection coefficient in order to record data".
A different technology from rewritable-type "BD-RE" discs is used for write-once-type "BD-R" discs. Since the recorded data will not be deleted, the most common method involves exposing the disc to strong laser beams to write markings that will not fade.