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Mark Cannell wrote:

>This is an interesting idea. Are you saying on your confocal that the
>light that illuminates the rear aperture has a narrower radius than the
>field stop -and that you can see the entire beam profile?

Not, it's not that bad.  But even on the Leica which has an adjustable
expander you're obviously not filling with a "uniform" beam but a
Gaussian.  The proof is the effect of opening the pinhole on lateral
resolution.

 I'd say on
>our system that the beam FWHM is >> the width of the rear aperture (we
>can't see the whole beam because it's clipped by stops elsewhere and it
>ends up as a more or less uniform circle of light about 1.5cm across).

There's a lot in that 'more or less'!  Try the experiment - see the
effect on your beads as you go beyond 1 Airy.

>My argument for opening the pinhole a bit when using deconvolution would
>be that as the pinhole is opened sub resolution beads get brighter.

If that is the case then something is wrong - probably SA.  They should
not get brighter by any greater amount than the increase in background
(plus the intensity of the first ring) and on our systems they don't.
Indeed, if everything is correct how could they?

Thus
>photons from the focal plane are being lost. Recovery of those photons
>in a photon noise limited system should improve final image quality -if
>resolution is being limited by shot noise..

The only way those photons can be lost is by aberration enlarging the
Airy disk into a circle of confusion or misalignment of the pinhole -
what else is there?

                                                        Guy

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