question about the laser in blu ray and DVD?

[OzamaBinLaden]

why does tha blu ray use a blue color laser ?
and why does DVD use a red laser ?
and why did HD DVD use a green laser ?

is tha blue laser supposed to be faster or something ?
and the red one slower ?

does tha color of the laser mean speed or density? etc etc

and for me to be able to play a movie on a blu ray disc, do i need a special edvice for it ?
can i play it on a normal DVD ?

 

[zoer]

The first LED lasers were red (even infrared, I think), and for quite a few years they were not able to make LED lasers that were higher frequency. The color of the light is determined by its frequency, Red=lower frequencies, Blue/Green=higher frequencies.

The higher the frequency of the light, the shorter the wavelength. Shorter wavelengths can distinguish smaller objects than long wavelengths - so the resolution of a blue laser is much higher than the resolution of a red one.

By increasing the resolution of the laser, it allows the data "bits" on the disc to be smaller, and therefore you can fit more information on the same size of disc. The information density goes up. Data on a disc is a long sequence of small "holes" or pits on the surface, that the laser "reads" like an old phonograph.

Blu-ray and HD-DVD discs have much more information on them than standard DVD (as DVD was better than CDs).

For a Blu-ray disc, you'll need a Blu-ray player - but it should be able to play a standard DVD, since the DVD is easier for the laser to read.