I have some questions

[MeGaBlitz]

Hello!

I am from Austria and tomorrow i am having a presentation about Blu-ray and HD-DVD. But i have so many questions and if i know something there will be tow more questions *lol* Please can someone answer the following questions?

1. Why is the protection layer of a Blu-ray disc smaller. Ist a HD-DVD safer than a Blu-ray disc? And if not, why is HD-DVD having a 0.65 mm layer? For what hat ist this layer using?

2. I have a list where is standing that the Numerical Aperature(NA) is 0.85. But what? mm? And i really don't know what it is. In another threat Marwin worte: "A unitless measure of the ability of a lens to gather and focus light." I don't understand this sentence. I can't translate it in German. Can someone describe this sentence for me?

3. Why will HD-DVD only be in a double-layer disc. Why not also multi-layer?

4. Which format releases first? HD-DVD or Blu-ray?

5. Is it right that Windows Vista will only be compatible for HD-DVD?


I would be so happy if someone could answer this questions for me. Thanks!
meGa

[AV_Integrated]

1. The protection layer is the distance between the surface of the disc to the layer that contains data. To increase storage capacity, BD puts the data layer closer to the surface.

If you abuse your discs, then HD-DVD may be safer. But, we have yet to experience this as a real issue. A scratch is very thin and can damage both formats equally.

BD has a added protective coating that may help reduce scratches and make it superior to DVD, HD-DVD, and CD for scratch resistence. Very cool.

2. ??? Nanometers? I am not sure.

3. I am unaware of HD-DVD being limited to dual layer, but the specification may only call for that right now. I believe it may be able to have more. I am not positive.

4. HD-DVD will be the first released in the USA by a couple of months. In Japan, Blu-Ray has been available for several years!

5. No. Vista may come out of the box with some added HD-DVD compatibility, but software drivers will be included with any Blu-ray Disc drives that are shipped. It should not be an issue.

Anyone here speak German fluently?

[MeGaBlitz]

yeah if someone speaks german, it would help but i understood all of your text. Thank you! But i really can't understand that Blu-ray relesed a few years ago in japan. why hab i never heard that before? I read only since a few months something about BD.

Thank you for your answers!
meGa

[MeGaBlitz]

Oh i found a picture of a tripple-layer HD-DVD. ANd i thought that there will only be ouble and single-layer discs:
http://img.lenta.ru/articles/2005/10.../hd-dvd-45.jpg



mvg, meGa

[thunderhawk]

Originally Posted by MeGaBlitz

2. I have a list where is standing that the Numerical Aperture(NA) is 0.85. But what? mm? And i really don't know what it is. In another threat Marwin worte: "A unitless measure of the ability of a lens to gather and focus light." I don't understand this sentence. I can't translate it in German. Can someone describe this sentence for me?

As Marwin wrote: A unitless measure, it's a proportion.
English article:http://en.wikipedia.org/wiki/Numeric...#Laser_physics
German article: http://de.wikipedia.org/wiki/Numerische_Apertur (but there's nothing about laser optics there, or am I wrong?)

Originally Posted by MeGaBlitz

3. Why will HD-DVD only be in a double-layer disc. Why not also multi-layer?

HD DVD isn't designed to be multi-layer. It's limited to 3 layers, totalling 45 GB in the end. However, this idea hasn't left the lab by my sources.

Originally Posted by MeGaBlitz

5. Is it right that Windows Vista will only be compatible for HD-DVD?

Ofcourse that's nonsense. And I don't see what the so called 'HD DVD support' is... Or what it's supposed to mean, except propaganda. >=(

May these sites help you...:
www.FreeTranslation.com
www.WorldLingo.com
Babel Fish

[MeGaBlitz]

Wow thank you for your help. It will help me very much for my presenation tomorrow. And thank you that you tried to understand my bad english

mvg, meGa

[Marwin]

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.

[Marwin]

Here you can see that the data layer where the laser is reading/writing is in the middle for DVD and closer to the surface for Blu-ray:

DVD:


Blu-ray:

[Knight-Errant]

Hopefully the harder coating of BD will mean that the data layer is just as, or even more protected.

[AV_Integrated]

I'm not sure I've EVER seen a disc with a data layer that has been damaged. Scratches are always the primary issue and they are very, VERY thin scratches. I expect the same issues with scratching may occur to both formats, but if Blu-ray incorporates the hard coating, it may make their discs more durable in the long run.

[crazy_neutrino]

Hi,
Sorry for my late answer, I need to work from time to time…but I tried to share my knowledge although might be a bit late for MeGaBlitz

The light that is reflected by the metallic layer of the disc is collimated by the objective lens on its way back to the optical system. During the read out of data the detection system can determine whether a "zero" or "one" is read, based on a priory knowledge about the difference between reflected intensities when the spot is focussed on a pit or a non pit. And now the magic word: spot…
This spot is formed by means of focusing a parallel beam with a system of lens. The geometrical assumption that a parallel beam that is incident on a positive lens converges into a single point is not longer applicable. This spot has a diameter proportional to a wavelength (405 nm for blu-ray for example) and inverse proportional to the NUMERICAL APERTURE OF THE LENS.
Diameter = wavelength/Numerical Aperture
As a conclusion, in order to have an optimal spot (almost punctual for a good distinction between pits and non pits) one needs a short wavelength and a large Numerical Aperture of the lens. One more time, the numerical aperture is a physical property of an optical system, like the focal distance for example. It is dimensionless (Dimensionslose).
What does it really mean this Numerical Aperture? It is the product between the index of refraction of the medium in which the lens is working (dimensionless and in the case of air equal to 1) and the sine of the angle between the outer ray and the principle axis of the objective lens. It describes the ability of an optical system to capture a beam with the condition of a good resolution.

Concerning the cover layer in blu-ray manufacture:
The cover layer has to be 100 micrometers thin, to fulfil given optical properties and to be scratch resistant. Additionally the layer has to be very homogeneous (3% homogeneity). Before wondering about the resistance of the cover layer lacquer one shall try to answer the following question: what kind of methods are available to bring the lacquer on the surface of a disc, to respect the requirements (especially the homogeneity and the thickness) and how to dry’it. Usually the drying process takes place under UV light. The lacquer has the properties of getting very strong (resistant) under this procedure. If you want a similar example think of a dentist and the way he’it repairing your plumbs.

Best!

[MeGaBlitz]

It's not too late. I had my presentation yes, but im very interestet in this next-generation-dvd-war and so every answer could teach me more and more. Thank you also for this late answer It's very interesting how it works.

thank you,
meGa

[thunderhawk]

How did it go?

[MeGaBlitz]

it was perfect! They were all very interested to Blu-Ray and HD-DVD I had got the best mark (in america it's an A, right?)

So thank you for your informations!

mvg, meGa

[Marwin]

That's great, and no problem at all