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Marwin · 03-06-2006, 08:14 PM

1) DVD and HD-DVD has the data layer in the middle of the disc (with a 0.6mm protection layer). HD-DVD changed the wave-length from 650nm (red laser) to 405nm (blue laser) to increase the capacity to 15GB per layer. The only way to increase the capacity further without changing the wave-length is to increase the numerical aperture (NA) of the lens. However, that requires moving the data layer from the middle of the disc closer to the discs surface, which is what Blu-ray has done to achieve 25GB per layer. The protection layer is as thick as it can be based on where the layer with the actual data is (0.1mm from the surface). The durability should be the same or better for Blu-ray as they will apply a hardcoating to the discs to protect them from dust, scratches and fingerprints.

2) The numerical aperture (NA) is unitless as stated in the previous thread, it's just a number that doesn't have any unit associated with it if I'm understanding it correctly. I think it means the ability of the lens to focus the light with greater precision, the greater the NA the greater precision.

3) The HD-DVD format is suffering from the same limitations as DVD, it wasn't designed to be multi-layer. I'm not sure exactly why they're unable to create multi-layer discs, they have created a prototype 45GB triple-layer disc but they're not able to do it in a cost effective way so it will probably never be used.

4) HD-DVD will be first with Toshiba's HD-DVD player on March 28. Samsung will release the first Blu-ray player on May 23 with Pioneer and Sony following shortly after.

5) Microsoft for some reason prefers the HD-DVD format, so in an attempt to publically boost the formats status they've stated that they will support it in Windows Vista. However, this shouldn't matter as third parties will release Blu-ray players for it anyway, just as DVD support isn't built into Windows XP and requires third party DVD players to be installed.

As to Blu-ray being released a few years ago in Japan, that was only a few select companies (Sony, Panasonic, Sharp) that released a few Blu-ray recorders for recording HDTV. These recorders were very expensive and not really targeting average consumers. The recordable/rewriteable specification has been finished for a long time so releasing products based on it was no problem, but the BD-ROM specification and copy protection has only just been finished for the playback format which will be used for movies.

03-06-2006, 08:14 PM	#5
Marwin Developer Top contributor Member since:May 2003 Blu-ray collection:10 DVD collection:5 iTunes collection:1	1) DVD and HD-DVD has the data layer in the middle of the disc (with a 0.6mm protection layer). HD-DVD changed the wave-length from 650nm (red laser) to 405nm (blue laser) to increase the capacity to 15GB per layer. The only way to increase the capacity further without changing the wave-length is to increase the numerical aperture (NA) of the lens. However, that requires moving the data layer from the middle of the disc closer to the discs surface, which is what Blu-ray has done to achieve 25GB per layer. The protection layer is as thick as it can be based on where the layer with the actual data is (0.1mm from the surface). The durability should be the same or better for Blu-ray as they will apply a hardcoating to the discs to protect them from dust, scratches and fingerprints. 2) The numerical aperture (NA) is unitless as stated in the previous thread, it's just a number that doesn't have any unit associated with it if I'm understanding it correctly. I think it means the ability of the lens to focus the light with greater precision, the greater the NA the greater precision. 3) The HD-DVD format is suffering from the same limitations as DVD, it wasn't designed to be multi-layer. I'm not sure exactly why they're unable to create multi-layer discs, they have created a prototype 45GB triple-layer disc but they're not able to do it in a cost effective way so it will probably never be used. 4) HD-DVD will be first with Toshiba's HD-DVD player on March 28. Samsung will release the first Blu-ray player on May 23 with Pioneer and Sony following shortly after. 5) Microsoft for some reason prefers the HD-DVD format, so in an attempt to publically boost the formats status they've stated that they will support it in Windows Vista. However, this shouldn't matter as third parties will release Blu-ray players for it anyway, just as DVD support isn't built into Windows XP and requires third party DVD players to be installed. As to Blu-ray being released a few years ago in Japan, that was only a few select companies (Sony, Panasonic, Sharp) that released a few Blu-ray recorders for recording HDTV. These recorders were very expensive and not really targeting average consumers. The recordable/rewriteable specification has been finished for a long time so releasing products based on it was no problem, but the BD-ROM specification and copy protection has only just been finished for the playback format which will be used for movies.