Blu-ray Disc (BD)

Before you start

Objectives: learn what is Blu-ray and different types of Blu-ray disks.

Prerequisites: no prerequisites.

Key terms: laser, dvd, drive, layer, read, blue, information, red, single, difference, double, format


Blu-ray Design

Blu-ray drive uses a similar technology as CDs and DVDs, however there is difference and that is the color of the laser used to read and write information from and to the disk. On a standard CD or DVD the drive uses a red laser. Blu-ray on the other hand uses a blue laser. The key difference is that the red laser has longer wave length than the blue laser. When we say wavelength we’re talking about the distance from peak to peak in the wave form of the light beam itself. While a DVD uses a 650 nm red laser, Blu-ray Disc uses a 405 nm blue laser diode. Because of that we can pack more information on the same disk. A single layer Blu-ray disk can hold up to 25 gigabytes of data. At the same time, a Blu-ray disk has the same physical dimensions as a CD or a DVD disk. Remember with a CD we’re talking about 650 and 700 megabytes, with a DVD single layer we have 4.4 gigabytes, and with a single layer Blu-ray disk we have 25 gigabytes. Most Blu-ray drives have blue and red laser built-in, so we can work with CDs, DVDs, and Blu-ray disks using the Blu-ray drive. Without this additional laser, Blu-ray drives would not be able to read CDs or DVDs. Blu-ray is intended to eventually replace DVD.

Blu-ray Types

Just as with DVDs, with Blu-ray we have a double layer option available. A double layer Blu-ray disk holds twice as much as a single layer Blu-ray disk (50 gigabytes). Blu-ray disks also come in read only, recordable or rewritable formats, just like DVDs. The read only format for Blu-ray is called BD-ROM. The recordable format for Blu-ray is BD-R, and we have BD-RE which is rewritable.

Speed

Just as we rate CD and DVD drives according to the drive speed, we also rate Blu-ray drivers. A 1X Blu-ray drive can read information at 4.5 megabytes per second. The 2X Blu-ray drive can transfer information at 9 megabytes per second, etcetera. For HD video, the minimum playback requires 2x speeds.

Remember

Single layer Blu-ray disk can store 25 gigabytes of data. A 1X Blu-ray drive can transfer information at 4.5 megabytes per second. Blu-ray disk has the same physical dimensions as a CD or a DVD disk. Blu-ray Disc uses a 405 nm blue laser diode.

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