Having recently been kicked out of a different thread due to the OT nature of the posts I have decided to make a new thread for AVScience enthusiasts.

So the rules of this post will go as such:

1. No bickering.
2. No trolling (i.e. my format is better than your because we have [insert film here] and you don't).
3. No arguing.
4. Scientific or technical information only.
5. Posts about either format are allowed.
6. No sniping.
7. Nothing and I mean nothing about prices unless they pertain to component pricing or replication (i.e. no MSRP discussions).
8. All data must be labelled as fact or conjecture.
9. Facts must be presented with corresponding real world data, links are fine as long as it is from a reputable source, and no, Wikipedia isn't reputable. Magazine scans are fine (as long as forum rules permit it).
10. Codec discussions will be allowed, but no negative input from certain members employed by a large company, sell me VC-1, don't try and turn me against MPEG2 or H.264.
11. Screenshots are fine for the codec discussions as long as they come from a direct feed using good decoders, and these should be listed with the screens along with timecodes so results are reproducible and verifiable.

I know it looks like a lot, but most of these are just common courtesy and shouldn't be hard to stick to.

So lets bring the science back to AVScience.

Scientific information on how blue-violet laser diodes are made:

Sapphire seed crystals are placed inside a CVD (crystal vapour deposition) chamber and GaN is deposited.

The process is incredibly expensive compared to normal methods, yields are terrible making the diodes produced very expensive.

Source - My lecture notes by Professor Kingsley Cavell.

One of the common problems BD in the early days was that the focusing mechanism of the blue-violet laser diodes for Blu-Ray was much tougher to do than HD DVD.

This resulted in much lower yields in the beginning, causing PS3 production shortage in the end of 2006, this in turn made all BD players extremely expensive. On the flip side, because of this ability to focus to smaller dots, the BD format not only has higher data density, it also has more headroom per layer to increase further data density. Higher data density typically allows bigger size and higher data throughput --- given the motor spins at roughly the same speeds.

Apparently, the yield problem is resolved, and 6 million+ drives (built) later, the cost difference may be closing more rapdily than some people expected. This in turn caused a glut of PS3s in stores that needed a $100 discount to move.

One of the common problems BD in the early days was that the focusing mechanism of the blue-violet laser diodes for Blu-Ray was much tougher to do than HD DVD.

This resulted in much lower yields in the beginning, causing PS3 production shortage in the end of 2006, this in turn made all BD players extremely expensive. On the flip side, because of this ability to focus to smaller dots, the BD format not only has higher data density, it also has more headroom per layer to increase further data density. Higher data density typically allows bigger size and higher data throughput --- given the motor spins at roughly the same speeds.

Apparently, the yield problem is resolved, and 6 million+ drives (built) later, the cost difference may be closing more rapdily than some people expected. This in turn caused a glut of PS3s in stores that needed a $100 discount to move.

The PS3 price reduction was caused by lack of sales not the number of units produced. Those numbers are very similar to the numbers of Xbox 360, and there has been no price reduction to date on that item. There also seems to have been a fairly consistant number of PS3s produced up to this point and the actual glut started in January. Whether there are better yields of BD diodes or there is just more production hasn't been answered that I have seen.

Is Sony still making all their own diodes?

Here's a fact - AVS Forum is named after AV Science, a retail store that happens to own and operate this forum. The name has nothing at all to do with the presence or absence of scientific discussion on the forum, and it makes me chuckle when people act otherwise.

The title of this thread says it's for scientists. So I hope we are going to implement a system of verifying everyone's academic credentials. :)

One of the common problems BD in the early days was that the focusing mechanism of the blue-violet laser diodes for Blu-Ray was much tougher to do than HD DVD.

This resulted in much lower yields in the beginning, causing PS3 production shortage in the end of 2006, this in turn made all BD players extremely expensive. On the flip side, because of this ability to focus to smaller dots, the BD format not only has higher data density, it also has more headroom per layer to increase further data density. Higher data density typically allows bigger size and higher data throughput --- given the motor spins at roughly the same speeds.

Apparently, the yield problem is resolved, and 6 million+ drives (built) later, the cost difference may be closing more rapdily than some people expected. This in turn caused a glut of PS3s in stores that needed a $100 discount to move.

Question: Given the information in the first paragraph, what is the expected long-term reliability of BD laser mechanisms given their tighter tolerances, especially given normal wear and tear in the average household? And how would this relate to the HD-DVD laser mechanisms?

Doug

The title of this thread says it's for scientists. So I hope we are going to implement a system of verifying everyone's academic credentials. :)
One doesn't need academic credentials to be a scientist. How many scientists are still in pursuit of a degree? Let's not be completely irrational or intentionally inflammatory.

Apparently, the yield problem is resolved, and 6 million+ drives (built) later, the cost difference may be closing more rapdily than some people expected. This in turn caused a glut of PS3s in stores that needed a $100 discount to move.

See rule #8.

The PS3 price reduction was caused by lack of sales not the number of units produced. Those numbers are very similar to the numbers of Xbox 360, and there has been no price reduction to date on that item. There also seems to have been a fairly consistant number of PS3s produced up to this point and the actual glut started in January. Whether there are better yields of BD diodes or there is just more production hasn't been answered that I have seen.
If you had bothered to read what I wrote, I said the price reduction was caused by a glut in PS3 in the stores. But the reason why so many PS3s could be made was because the diode yield issues were no longer an issue, and when yield issues disapppear, costs always go down.

The $100 lower price of PS3 is now causing them to move quicker from the shelves. Last month's PS3 outsold x360 --- this in spite of having almost no good games. To outsell x360, PS3 had to be priced < $100 more than the common (non-elite x360). To outsell wii, PS3 not only has to be priced < $100 more but also has to have innovative games, as it is the ground-breaking games and motion-controller that is selling wii, in spite of (weaker SD) graphics, and the price is not the only reason.

Back to the scientific part of this.. I'm not sure what the BD burners use to burn both DVD and BD. Are they using a single laser diode, or do they include both red and blue lasers? Does anyone know?

See rule #8.
Ah, but if there's still yield issues, there is no way millions of devices can be built. This is common sense.

Question: Given the information in the first paragraph, what is the expected long-term reliability of BD laser mechanisms given their tighter tolerances, especially given normal wear and tear in the average household? And how would this relate to the HD-DVD laser mechanisms?

Doug
This is one of those 'only time will tell' thing. I do know that HD DVD's don't last longer than chinese made DVD players under extreme stress, in fact, I'd say they start to fail earlier.

We have a few of HD-A1s used as cheap signal generators, at times, they run 24-7 for days, like the dozens of cheap walmart players we have. One started to fail within 2 months and fails to track properly. This is no more reliable than the $25 walmart players. We had to be more careful about device abuse after that and always power off unused remaining HDM signal generators after the 1st one failed.

The PS3 and single panasonic player are also used as signal generators, but we use it rarely and typically, only higher bitrate MPEG2 and AVC streams that won't play on the HD-A1 is played on the PS3 and panasonic, so they are not as abused as the HD-A1s.

Back to the scientific part of this.. I'm not sure what the BD burners use to burn both DVD and BD. Are they using a single laser diode, or do they include both red and blue lasers? Does anyone know?

For now, yes. Early DVD-ROM drives incorporated two laser-diodes, one for reading CD-RW, and a second for reading CD-ROM/DVD-ROM, and the optimum wavelengths for CD-RW vs DVD-ROM are a lot closer together than blue-laser vs red-laser. A few years back, CD-RW/DVD burners switched back to using a single-diode.

In a Bluray drive, I would consider the cost of the secondary red-laser diode to be insignificant. Ignoring diodes, the cost of the optical assembly (due to Bluray using a different Numerical Aperature), is still an area for improvement. Since Bluray for PC-storage is a potentially huge mainstream application, I hope mfgs find a solution!

We have a few of HD-A1s used as cheap signal generators, at times, they run 24-7 for days, like the dozens of cheap walmart players we have.

That honestly doesn't surprise me. Given the 'frankenstein' embedded-PC architecture of the HD-A1, the sheer # discrete components, high-heat P4 CPU, I'm surprised it was as reliable as it was. The failure-mode you cited, optical tracking problem, worries me, since the loader (i.e. drive) should (theoretically) be a separate entity from the rest of the player.

Question: Given the information in the first paragraph, what is the expected long-term reliability of BD laser mechanisms given their tighter tolerances, especially given normal wear and tear in the average household? And how would this relate to the HD-DVD laser mechanisms?

Doug

Don't sweat the diode yields. That's not a difference. The difference is the tighter pitch due to the focal length to the optical media, hence the storage difference. Tighter pitch means a more robust head is needed to support the structure.