Format #362 - Blu-ray/DVD Combo ROM Disc

[Audioholics]

<P><FONT face="Arial, Helvetica, sans-serif" size=2>JVC announced that it has developed the world's first Blu-ray/DVD combo ROM disc technology, which enables storage of video content in both high definition and standard definition. The new ROM disc, which has a total storage capacity of 33.5GB, uses a triple layer structure comprised of an outside Blu-ray disc (BD) layer and inner DVD dual layer (Fig. 1). The outer BD layer is capable of storing high definition video signals up to a capacity of 25GB. The inner DVD dual layer can store up to 8.5GB of standard definition video signals. During Blu-ray reproduction, blue laser read the outer BD layer, while red laser read the inner DVD dual layer during DVD reproduction. The triple layer structure was made possible by the development of a high-performance reflective film that reflects blue laser used for Blu-ray reproduction, but is transparent to red laser used in DVD reproduction. Whether this new technology serves as a&nbsp;main format, interim stop-gap,&nbsp;or even becomes formally adopted by the Blu-ray Disc Association remains to be seen.</FONT></P>
<P><FONT face=Arial size=2>[Read the Article]</FONT></P>

 

[howie85]

What is the signifigance of the different color laser?

 

[Audioholics]

The quick explanation is that it has to do with the size of the laser's wavelength and thus the size of the data "pits" that can be used to store data.

 

[howie85]

That is determined by the color or vice versa?

 

[Rob Babcock]

Remember learning "Roy G Biv" back in HS? It stands for the colors of the spectrum: red, orange, yellow, green, blue, indigo and violet. Red light has a shorter wavelength than blue. Infrared is literally "below red" and is too long to see. UV is shorter than violet and is too short to see. Blue lies in between and is one of the shorter wavelengths the human eye can perceive.

A shorter wavelength beam of coherent light (ie laser) can read a smaller pit than a beam with a longer wavelength, like the current red ones in todays gear. That's why Blu-ray is an advance over current DVD technology; in addition to more advanced data compression, it can simply fit more pits onto a given area.

The main disadvantages has been higher cost and a lower service life for blue lasers than for the red lasers in use now. The difficulty in creating an economical blue laser is the main reason Blu-ray has taken so long to get to this point.

 

[howie85]

"DING" your lights are on....

Something in the back of my mind was telling me that the color of the ray was determined by the wavelength. Thanks for the info. Sometimes you just wanna know why right?
by the way Rob thanks for posting the chili recipe I gotta try that