Re: [ATM] Phase contrast and the 10 incher.

["Arjan te Marvelde" <arjan.te.marvelde@hetnet.nl>]

Dale,

> saw kurf.  One of the worm tracks crosses over into
> the core.  So the worm tracks are probably either on
> or close to the surface.

How can something below the surface become visible? It implies reflection
(and focussing) of light from deeper layers.
Could it be reflection from the backside? Can you kill these reflections?
What happens if you precisely focus on the front surface, e.g. helped by
marking it?

Looking at the Foucault image, it still strikes me that the worm tracks are
so well visible, independent of location on mirror surface. If they were ON
the surface the image suggests severe surface distortion, multiple waves,
like the scratches. Also would they be visible in the 'black' foucault image
you posted, just like the other scatter sources (scratch,finger prints).

If the quiz is still on, I'd bet on sub/back-surface structures and bad
camera focus.

Cheers,
   Arjan

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