Re: [ARSCLIST] ? about Burning CDs for archives

[Don Cox <doncox@xxxxxxxxxxxxxx>]

On 22/08/04, Jerome Hartke wrote:
> Light is not "scattered" in the polycarbonate substrate.

Why not? What prevents it from being scattered?

> Diffraction
> and interference modulate reflected light from pits and lands of a
> replica. Recorded CD-R dye or CD-RW alloy layers directly modulate the
> reflected light intensity.

Sure, but during the photographic process of "burning" a disk, there
will be a proportion of scattered light, unless the polycarbonate is
optically perfect and its top surface is optically perfectly flat. Light
will be scattered from the groove which is used for guidance.

All this will affect the exposure of the photosensitive dye. What
exactly will happen at the end of an exposed "dash" ? There is a
threshold below which the dye is not exposed enough to change.

I see no reason why the optics here should be any different from the
optics of high resolution photographic film. The main difference is the
absence of a fixing process, which means the permanence of CD-Rs is
dubious.


Have you actually tested any black disks? What were the results?

Regards
--
Don Cox
doncox@xxxxxxxxxxxxxx