Re: [ATM] The zonal Foucault test is free ofinherentcorrection bias- some supporting graphs

["Richard F.L.R. Snashall" <rflrs@rcn.com>]

Richard Schwartz wrote:

> If you are doing a conventional pinhole and knife edge test, I think that
> parallax parallel to the blade edge does not matter. To understand how 
> this
> is possible, imagine that you are a God, an Angel, a fairy, or some other
> spiritual being, and you are hovering above and looking down vertically on
> the test from an infinite distance. Imagine that with your 
> superpowers, you
> can actually see the light rays. Now, if the pinhole moves up, and the
> focal point of the returned rays moves down, from your point of view there
> will be no change. Also, from your point of view, the blade edge looks 
> like
> a point.
>
> . . . Richard

I don't think I'm convinced by this... anyway you do it, if the two perfect
foci are at different points, the null conicoid is not a sphere.

However, if the source is a line (?wire test?), does the integration along
the line remove that difference.  Again, why would it choose a sphere as
the reference conicoid?
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