Re: [ARSCLIST] Optical disc "repair"

[George Brock-Nannestad <pattac@xxxxxxxx>]

From: Patent Tactics, George Brock-Nannestad

Hello,

I have visited the website of Azuradisc, and I think that it is reasonably 
well documented. There are no independent tests, but I do not see Jerry 
Hartke's arguments against these processes as entirely convincing.

Optical polishing is the final stage in optical grinding, and that does not 
usually leave millions of microscopic scratches, at least not on glass. When 
working on plastics, obviously the polishing materials and the process 
parameters have to be different.

The actual physical distance between the reflective layer and the objective 
lens is only of importance if a substantial thickness of polycarbonate is 
missing, because of the focussing servo, which adjusts for variations up to a 
certain maximum variation per second, such as that occurring with a wobble. 
The Audio Development CATS for stampers has a glass window that is applied to 
compensate for the spherical abberation due to the completely missing layer 
of polycarbonate. But then, they need much more from the received signal than 
mere replay. Someone with time left over on a CATS (and the money to pay the 
operator) ought to perform the tests Jerry suggests. Perhaps Consumer's 
Union?

Kind regards,


George

-----------------------------------------------

Jerry Hartke wrote:


> Very few suppliers of "repair" products or services use an independent
> testing lab, such as ours, to validate their claims. I would expect
> disappointing results.
> 
> Burnishing generates millions of microscopic scratches that act as a
> diffraction grating and can degrade the laser beam. Burnishing also thins
> the disc, which is undesirable because the distance from the entrance
> surface to the information layer is carefully matched to the objective
> lens
> in the drive. This lens predistorts the beam to compensate for the
> refractive index of the polycarbonate layer, and the result is sensitive
> to
> the thickness of the polycarbonate layer.
> 
> Best to replace a damaged disc or to make a copy while it is still
> readable.
> 
> Jerry
> Media Sciences, Inc.
> 
> > -----Original Message-----
> > From: Association for Recorded Sound Discussion List
> > [mailto:ARSCLIST@xxxxxxx] On Behalf Of Marcos Sueiro Bal
> > Sent: Thursday, February 07, 2008 11:02 AM
> > To: ARSCLIST@xxxxxxxxxxxxxxxx
> > Subject: [ARSCLIST] Optical disc "repair"
> > 
> > On my way to work this morning I was intrigued by a poster in the local
> > game shop advertising CD and DVD "mail-in" repair. I went to the web
> > site listed. Take a look around; it is fascinating, among other things
> > because it is directed towards dealers selling the process.
> > 
> > http://www.azuradisc.com
> > 
> > I have heard at least one expert in optical media state that all of this
> > burnishing systems are actually damaging the polycarbonate layer and are
> > harmful in the long run, but I wonder if there are any papers showing
> > any reduction of errors after this kind of process (good luck finding
> > links to such a paper in the web site above). If so, could process like
> > this one be compared to, say, baking of tapes? In other words, "get the
> > data to another medium while you can"? (But note that this is not what
> > they advertise in the web site; they advertise actual repair of the
> > disc... it will be like new!)
> > 
> > There are accessories sold by this company (e.g. foam for your jewel
> > case?!?) that make me suspicious, but I am not ready to condemn their
> > whole process yet. I am curious to hear reactions or comments from other
> > posters.
> > 
> > Cheers,
> > 
> > Marcos Sueiro
> > Columbia University